Cramps?

So I've been having dull cramps on my right lower abdomen on and off for awhile now. They don't really hurt they just are like a pulling sensation. My doctor reassured me that it was just the stretching to make room so I was relieved. Well tonight I had a really severe cramp that started on my right side then traveled to my left then started to settle before picking back up again on both sides and in the middle. It lasted about twenty minutes. I also had the sensation of needing to start a period so my stomach dropped and I thought, "oh dear God a MC" there was no bleeding though and it went away. I feel fine other than the normal symptoms but now I'm worried. What if it's ectopic? All my lines are faint and barely increasing in color. The first was so light I thought it was an indent and that was the first day of my missed period. I am 4 weeks 4 days now and am worried. I called my doctor and she said that it was perfectly normal to have cramps but I don't think she understood my description of them. I'm worried this baby won't stick and I don't want to go through a MC again. Does anyone know what could cause a cramp like that? Has it happened to any of you? What do all these faint lines mean? Any insight would be much appreciated. Thank you for your time. I'm posting this on general pregnancy too to see if I can get some extra insight. Sorry if you see it twice.