How do you know when it’s contractions

I’m sure if I’m having them it’s just Braxton Hicks because there not super painful it just feels super tight but how do you know when it’s contractions and not the baby just pushing against your abdomen? I think I’ve been having contractions all night and the pain seems to be getting worse (as far as I now have cramps and lower back pain) but I’m still wondering if it’s just baby pushing against my abdomen so how can you tell the difference between the start of labor and just the baby? Btw I 38 weeks with my first