Braxton hicks with twins?

How early were you when you started feeling BH? I'm currently 20weeks+5 and think I've been feeling them on and off for weeks! My OB said it was too early but my mfm dr said it wasn't too early for twins! Some days I think I feel them all throughout the day and some days I don't feel anything! I also don't know if it might be just growth spurts when I think I feel them because my belly just feels more huge some days (usually the days I think I feel BH)!  My OB said it's probably just round ligament pain, bc that can also feel like tightening?!? But what I've research what I feel, feels more like Braxton hicks.  Any advice on BH while carrying twins?!?