How to get baby to sleep in crib?

So my son is 3 months old, he has horrible reflux. Hes constantly throwing up, he slept in his bassinet alone for his first week but we barely got sleep. He wont sleep flat, he wakes up screaming every half hour covered in puke. On nights my SO is home for he just stays up all night with him because we dont want him to sleep in a swing or anything. And I really do not want to co sleep but that seems to be the only thing that works when we have to sleep. I've taken him into the doctor 4 times but they tell me it's normal. I have an older child and he slept in his crib just fine so I'm really at a loss.