If they get longer, stronger and closer together then I would for sure call the drs office. But until then it could just be false labour
Maybe call your doctor and see if they can get you in today. But if they do get closer together, definitely head to the ER especially if it's after your doc office is closed.
If you get 6 or more braxton hicks an hour then you should be calling your Dr. But other then that it does not mean you are going to have pre-term labor. Heartburn happens to a lot of women, especially in the 3rd trimester--I have been getting it since about week 20. Braxton hicks is your body practicing and getting ready, I am 35 weeks and I have had some days where I will get a lot and some days without any. Pressure down below also happens in the 3rd trimester since the babies will start moving their way down and the back pain is not uncommon either because of all the extra weight you are carrying. You of course want to talk about all this stuff with your Dr. especially since you are carrying twins and are more likely to go early, but all of these things are normal. Good Luck!
I think your fine, but when you get horrible lower pressure, And feel like you gave to poop for a Long shile, And.cant, that could be a sign.