Contractions are, as nsrchofbaby wrote, tightening of the lower abdomen. This usually lasts (at our stage they are Braxton Hicks contractions) about 30 s. A friend of mine never noticed them (alot of women don't) but I have been getting them since the 5th month and I notice particular situations where I get them e.g. after being on my feet for a long time, walking fast. Period like cramps are normal but if they radiate to your back then usually it isn't. My stomach is also hard most of the time, but my little one is pressing against it most of the time which is usually the reason why.
A contraction is a tightening of the uterus, not the "hard" feeling of the stomach. My stomach remains firm pretty much all the time as well but it's become kind of an obvious difference when I have a contraction, it's visible. It's like a bump on top of a bump. If you're experiencing cramps that don't subside you need to contact your dr as you may be experiencing pre-term labor and at 35 weeks you would do best by keeping baby in there longer to allow time for lung maturity.
I am currently 35 weeks, so I am due very soon June 17th. The thing with me is that my stomach feels like a tight ball all the time. Even my doctor was surprised that it stays hard all the time. I just wanted to know if contractions feel anything like cramps.
Braxton Hicks contractions feel as though your stomach tightens into a ball with pressure and can last for about 45 seconds. They're usually not painful and occur with no regularity. True labor contractions will consist of the same process (uterus tightening) but will be accompanied by pain that radiates either from the top of your uterus down to the bottom or from your lower back through to the front. True labor contractions will become more and more painful and will be consistent despite changing position. Cramping throughout pregnancy is normal. If it becomes severe, contact your dr. ASAP. When are you due?