I need help!!

My son is about to be 6 months old, for the past week or so he’s been fighting to go to sleep at night and it’s been HORRIBLE! He used to be a perfect sleeper but lately he is a completely different baby when it comes to putting him down for bed. I feel so bad for feeling frustrated but I just don’t know what to do! Please tell me I’m not alone and if anyone has any tips to make bed time go smoother PLEASE SHARE THEM!!!