N.C.
My sons both did the same thing. They are now 19 mo and 3 y. 1 mo. My pediatrician's recommendation was to give him a bottle of water (not cold, not too warm) instead of nursing, to avoid the "feed-drift to-sleep" trap. I found that if I did nurse, he continued to wake up. But if I let him cry, it didn't last for very long (20 or 30 min. max at the start, then it dropped down to just a few minutes over time). I did find that giving a larger bottle of formula before bed made a difference, so long as he had a good burp afterwards. Also, try putting him to bed a little earlier. It sounds odd, but an earlier bedtime often results in sleeping longer. My 19 mo started going to bed at 7pm instead of 7:45 pm, and that helped a lot. Also, has he outgrown his current diaper size? That was a big reason both boys started waking up at night--too wet, although not soaked through. Also, this is typical for a 5 month old, so don't be afraid to try different approaches--and keep a log, hard as that is--to see what combination of eating/drinking/bedtime seems to get the most consecutive hours of sleep. I'm still up 4 nights a week with one or the other one for some reason, but I promise you it does get better and it will pass. For now, crying it out is a great place to start if you are comfortable with it. Amazing as it is, our two started sharing a room at Thanksgiving, when my toddler was 16 months and still waking up nightly due to teething. And yet 3 months later, despite many nights of screaming fits, the toddler never woke up my preschooler. They seem to build up an immunity to the noise that we as moms seemingly have to avoid developing! Good luck!