12 week old won’t sleep in his cot!

My 12 week old won’t sleep in his cot and we end up co-sleeping which I’m really hesitant to do. He has had weeks when he has slept in his next to me cot. He is breastfed. We have tried everything, putting him in awake, half asleep, fully asleep. Putting him down feet first and gently removing our hands but keeping one on his chest for a good time. Using blankets or a sleep bag. White noise, nothing seems to work. Anyone have any ideas? Or some reassurance this will get better 😩 I don’t sleep well when he’s in bed with us and I’m feeling exhausted!