Late for 2 cycles.. Never been pregnant before

I have been late for 3 cycles now, last month we went to the doctors for bloodwork and an ultrasound, they didn't find anything. About two weeks ago I took a test because my breasts started getting extremely sore, and still are now. Haven't taken a test since, I'm not sure why my breast would be this sore tho. Usually they get slightly sore before my period but only just slightly. I hate to take a test and it be negative again, but I just want to know why I'm late. I also have had slight cramping but it only lasts about 10-30 seconds throughout the day maybe 20 times a day. Anyone else have a similar experience? I've never been pregnant before so Any advice would help. Thanks!