Honestly, it seems like your little guy is going through a transition of some sort. This age is a big turning point. The world is coming into better focus, he is getting stronger, maybe trying to crawl or pull up, growth spurt is BIG around this age. All of that = NO SLEEP! Seriously. When babies are learning emerging skills it is like they are in a hyper alert stage. They wake up and want to practice! Also, big growth can happen at this age, which means LOTS extra calories are needed.
I know it sucks. Trust me. I know! My daughter was 14 months old before she slept 10-12 hours through at night. Oiy. I am not a cry it out mom before 12 months at least. Before then, I feel very strongly they NEED to know and be reassured that we are there for them. Once they hit that 1st birthday, and (depending on the individual child) really understand that even if they can't see us, we are there and WILL help them .... that's when I will try the CIO. That is what we did for our daughter. It took 3 nights of less then 5 minutes each night of her crying, and now she sleeps through no issues. Unless of course she is going through a growth spurt and then all bets are off. Oh, and in case you worry that not letting him CIO will cause him to be clingly and needy. Nope. Giving your child the assurance that you are there for him will help him feel confident to explore and do things on his own. He will know that if he needs you ... you are there.
Here's an interesting tidbit that my Certified Nurse Midwife told me. She said there was a study done to see 'how' kids grow. Do they grow all at once, or a little here and a little there. The study found that LITERALLY overnight a baby can grow 1/4 or even a little more!! That's incredible!!! So, not only do they need extra calories...but if your body is growing THAT FAST ... that has got to cause some discomfort!
When he wakes up, what does he seem to want? Try feeding him. Try just reassuring him. Be calm. Be soothing. Say things like "it's still night night time. It's still time to sleep."
In my experience with my daughter, growth spurts lasted 4-6 weeks. Then we would go back to our regularly schedule program. :-)
Make sure his needs are met. Make sure that he knows you will be there for him. Unfortunately, the first year is pretty much hit or miss with the sleep. It's just the way it is. It's a huge year for transition for baby and it all disrupts the sleep pattern. Power through is about all I can tell you to do. It will pass. It WILL get better. :-)
One thing, as you feel he is coming out of the growth spurt, or whatever it is that is waking him up (emerging skills etc...) make sure to be consistent with the soothing "it's still time to sleep" routine. They can get into the habit of waking up even once the growth spurt is over. Be calming and soothing...but try to not stimulate him too much. Don't talk alot...just be there. Rock if necessary, but not until he is completely asleep. Don't do the same thing every time. Sometimes soothe him in his bed, sometimes rock, sometimes just hold.... you get the picture. Less likely to form a habit that way.