Contractions ?

I’m currently 35 weeks and 2 days pregnant and I have been experiencing contractions for 4 days now. Last night was the worst ones, it woke me up from my sleep and kept me up until 3 am. I feel like it tends to get worst during the evening and at night. It’ll get real tight around my belly button area and then the cramps will come afterwards. I time it last night and they were 3-5 mins apart lasting over 2 hours. I had to force myself to sleep through it. I tried switch positions and it didn’t help. Should I call my OB and let her know? Or is this just Braxton-Hicks? Any ideas ladies....