membrane sweep

Ah
How soon can you ask for one? I feel like I'm right on the edge of labor but this is taking forever. Baby was low enough for my dr to easily feel his head and I'm 2cm 50% effaced as of yesterday. had my bloody show on Saturday. I'm getting impatient. Ive had a bunch of contractions that I can time but they don't get stronger. I've been having period like cramps now since 9 last night and it's 12 pm the next day. Wtf 
I'm 37&3 today.