I went through the exact same thing...dd would not nap longer than 45 minutes (if we were even lucky enough to get a nap). I tried playing with her awake times, and when 5 hours had passed and she still wasn't napping, I knew we had a problem. I don't know how your baby sleeps, you didn't mention if sleeps independently or if you have to put him to sleep, but in my case, we did pu pd for her, and she started sleeping on her own. Initially, it was still short naps, but she learned to sleep for longer stretches on her own. I hope this helps.