Braxton Hicks

So I'm 28 weeks and as of 5 days ago, I've the been getting braxton hicks contractions.. I guess they could have started earlier than that and I didn't notice.

Anyway, I guess my question is (for those of you experiencing them) how often do you feel them? They're painless, just really tight and pretty often - the other night I had about 6 in an hour. I see my midwife next week but thought I'd check on here!