K.M.
Hi J. -
My best advice to you is NEVER to let your son "cry it out". It makes him feel bad, it makes *you* feel bad, and it really doesn't do any good for anyone. I don't know exactly when this school of thought began, but there are definitely those who will tell you that your child "needs" to learn independence, to be on his own - and I've always found this notion to be utterly ridiculous. Your son is still a BABY. He needs you, he relies on you. Don't be in a hurry to break that bond you have now, because it's only going to be a couple of years before he starts saying "I don't need your help, mommy!"...
Anyway, with that said - your son sounds exactly like mine. And mine went through the same phases; there would be a week when he would sleep for 10 hours straight and we'd be relieved, then for 2 or 3 weeks he'd wake up like 5 times a night. It's normal. It's exhausting at times, but normal. If it seems to help to let him sleep in your bed, do it. I promise you that it will not last. People are quick to say that such behavior lays the foundation for bad habits later, but I've found that this is largely untrue. Yes, babies are clever, but your son is not manipulating you. He'll outgrow it, and it won't be long before you find yourself wishing to be back where you are now...
(My son just turned 4 in January - and already he doesn't need my help! LOL. It makes me a little sad sometimes now, because I remember being in a hurry in the beginning, too - When will he sleep? When will he eat real food? When will he potty train? Then it seems like you blink and it's all over!)
*EDIT: I just re-read your message and noticed that your son is asleep by 9pm. This seems pretty late to me. I know it sounds weird, but your son may actually be having trouble sleeping because he's a little sleep-deprived by the late bedtime. I would try to get him in bed closer to 7pm...