FTM Question...I don't know how to recognize my son's hunger cues?

I feel at a loss. I'm paranoid I'm under feeding my baby. I introduced solids late around 11 months. My son was 10 weeks premature so my mom advised I keep to formula as long as possible. Anyway, my son is almost 13 months. I took him off formula at a year, but ever since I'm not sure if he's full, I worry I wait too long to feed him but then I worry about overfeeding him. He won't hold his own bottle and I think I messed him up by not letting him self feed. Have I ruined his eating habits long term?