I can do only down strums and sing, or do a strumming pattern like Old Faithful and play, but I can’t sing if there are is any pattern with up strums. I never realized most of my singing is on the down beat. So as soon as I add an up beat it throws me off.
Do other people experience this? Any suggestions for how to get past this?
Craig, there are those in the Community who make playing and singing seem easy. I still find it hard and there are songs where it clicks and others that I just struggle. But I have found over the years that slowly it gets better. Working through Chris Liepe’s Discover Your Voice helped improve my singing and also my playing and singing, which was a little unexpected.
Craig. You are not alone in finding it difficult to combine singing with playing. It takes patience for sure. Once you burst the bubble you will find a freedom that allows you to explore much further.
Your singing? Your own songs & lyrics? Or covers of well-known songs?
If the latter I would encourage you to put your guitar down and listen with a really attentive ear to the phrasing used by a range of vocalists. Listen to a song, focus only on the singer. Listen again and try to count along. For the second listen you are trying to figure out when vocal phrases begin. I think you may be surprised at how many of them do not begin on the count of 1. You may find many begin just before the 1 or on the 2.
Hey Craig - I used to be a motorcycle instructor …stay with me, I’m getting to guitar … students starting out would spend almost all their attention on the clutch, there was nothing left to think about traffic, brakes etc. An experienced motorcyclist spends almost no attention on the clutch and can focus on their surroundings.
Now, I’m no expert with singing or guitar, but I think it’s the same learning anything new. While you are thinking about your strumming and patterns then that takes up some of your attention, leaving you less to be able to think about singing and phrasing.
As Richard and David have said, it will improve. As your strumming becomes more automatic then you stop thinking about it and things will fall into place. I was recently learning a new song that had a complicated (for me!) strumming pattern, and I couldn’t sing to that until I had trained that pattern to be automatic. The longer you stick at it, the quicker that learning happens, but it still takes time.
You will get there.
Foot shifts and good timing ! Great analogy Paul. Get the playing on auto pilot before even thinking about singing, took me decades to do both ! 
I know that everytime I try to sing , my rhythm seems to go outta whack…for most songs. However there are a few that I can now keep the rhythm and ‘sing’,if you can call it that!!! Lol. Not crazy bad, but certainly not good. Taking me mega practice to be able to. To be honest I concentrate mostly on solid rhythm, making it feel good while super relaxed and making sure I hit the 1 beat and accents on 2 and 4…well that can change sometimes but it’s a solid foundation.
Rock on brother!! 
Hi Craig, I think what you describe is pretty normal and happens to many, it surely happened to me. The reason seems pretty simple to me: the down strums tell you clearly where you’re in the bar, while upstrums usually messed things up for me. My suggestion: listen to the original recording, sing and tap your foot along as many times as you can. Can you do that? Then play the pattern tapping your foot on the beat and make it automated, always tapping your foot, but without singing. If you can do this too, slow the tempo down as much as needed for you to be able to play, tap and sing at the same time…it might get sometime but it will click, you have my word 
just go slow and smile, being relaxed is key!
Back-up plan…just in case…put the recording on, mute the strings with your left hand, sing along and wild-strum along…it’ll get you in the groove without thinking of up or down strums, it’s such fun to do and make you feel good and relaxed and…the happy circle you need has started!
Hi @moose408, I see you only started in June this year. Being able to sing and play at the same time after only six months is good going. All good advice already by others so I am not going to repeat it, just wanted to add to the reassurance that it’s normal to struggle for ages with this.
Not to sound blithe about it, but I think it’s a matter of just keep doing it, keep practicing it. Go slooooooow, as Justin said. Pick up speed later. It will become something you no longer think about, you just do. Those kinds of things seem to happen all of a sudden. You keep doing it and doing it and doing it, again and again. Lots of failure, mistakes, awkwardness. But we keep doing it, and then one day … For some, it happens quickly, for some it takes time. There is little we can’t do, I think, if we just keep practicing, making mistakes, and basically just keep going. However painfully slow it sometimes seems we are going!
The cardinal rule: don’t quit!
I have nothing new to add from what others have said but just urge you to stick with it , and once your strumming (with up strums) becomes automatic you won’t even think about it and the singing will just flow.
I really struggled with this and thought Iw
Would never get it but did the strumming class and by practicing the strumming pattern with muted strings for 3 minutes a couple of times a day for a week till it became automatic I actually managed to play and sing ( of a fashion) 3 little birds. Since that moment I have done the same for any song I am learning and it really helps.
I think most people already gave better advice than I have, I’m still pretty bad at singing and playing. My approach when I’m really struggling: do the song a few times only adding the down strum on beat 1 until I’m comfortable. A few more times with beats 1 and 2. A few more times with all the down strums. When I’m comfortable with that, then I add the up strums. Sometimes it takes me days to figure it out. Be patient with yourself!