How do I get my 4 month old to fall asleep on his own?

So my son just turned 4 months old yesterday, and he does not sleep well at all. He is exclusively breastfed, and the only way I can get him to fall asleep is to swaddle him tightly and nurse him laying down in bed until he falls asleep then I have to gently put him in his crib without waking him up, if he wakes up in the night I have to do the same thing to get him back to sleep, even though I'm sure he isn't hungry. I try to do all the same things and gently wake him up before laying him down in his crib, but he just cries and cries until I pick him up and either rock him in the rocking chair or nurse him again (even though I'm sure he isn't hungry). My mother says I should just let him cry but I've read that its not good to do that until they're about 7 months, and I really don't think I could stand to do it right now. I've read that for a baby to be able to soothe himself back to sleep in the night its important for him to fall asleep in the same place he will wake up. I really need some advice on this, because I can't keep waking up 3 or 4 times a night with him, he is not a newborn anymore.