My 7 month old won't sleep in his crib?

I have a 7 month old baby boy, and he absolutely won't sleep in his crib. My boyfriend and I are deep sleepers, and I've always been scared to put him in his crib in another room for the fear I wouldn't hear him if he cried. So, we've kept him in his bouncy seat that lays back. Now we feel that he's way too old to keep sleeping in that thing, so we're wanting to move him to his crib, but it seems that he cries and cries when he goes in. If he's asleep when I put him in, he instantly wakes back up and starts crying. I feel horrible letting him cry it out too. Any suggestions? Thank you!