travelmumma, not to alarm you but if it were me, contractions that feel like that would be a red flag if there were more than a few of them in a day. I would contact my care provider (although I know you don't have one to contact right now ) or go to the ER.
I think tropicana is right, though, that everybody's different.
For me, "BH" are not painful, although they can kind of take my breath away. For me, when I get concerned is when at the peak of the tightening of my uterus I feel a sharp, poking kind of feeling very low, where my cervix is. For me, that means that there is probably some cervical change going on, which I DO NOT want to have happening at 18 weeks. I've had a couple of those so far, but only about once or twice in a day and then they go away. I've also had several episodes of what I would call 'crampy' feelings low down near my pubic bone that have NOT been associated with tightening of my uterus. I think both these sensations (for me) have happened because I was exhausted/stressed/and especially, dehydrated.
So if I were your doula and you called me to ask about this I'd tell you to take a nap, drink lots of water/electrolytes (summer) or decaf tea (winter), and go to the ER if you're having more than one or two in an hour or a half an hour or so.