My baby fought sleep at that same age, and nothing worked too. So I started sleep training, and we had to do the cry it out method (since other methods failed). You can read up on the other sleep training methods to see if you want to try anything, but if you’re going for cry-it-out, it gets a bit better after 2 weeks, and much better after a month, then there’ll be regressions here and there, but at least baby would have learnt the skills to self soothe.