For me, ligament pain came in two varieties:
1. the sharp stabbing pains already described, when I changed positions or moved suddenly, or coughed or sneezed
and
2. a dull ache, sometimes mild and sometimes really NOT mild, in my entire hip/pelvic/crotch region, usually at the end of the day or after I'd been on my feet too long-- sometimes on one side or in one area, sometimes in another
The second kind of pain seemed to be just when the muscles and ligaments and all that got TIRED supporting my uterus. I could distinguish those from actual contractions because my uterus would stay soft. A contraction causes the belly to get hard and tight-- if you put your hand on your bump, you'll feel it harden. A contraction comes and goes, but that second kind of ligament pain was constant. A BH contraction for me never came with any pain. When they hurt, for me, they were dilating my cervix (I had preterm labor with all my kids).
I used to get really alarmed about the pain, because nobody ever mentioned it, not in all the pregnancy books. You hear about the sharp pains, but not so much the achiness.
I found that just getting off my feet for awhile made it go away. When it got really nagging, I'd try to go swimming-- deep water will take the weight of the uterus, and give the poor aching ligaments a rest.