me and my girlfriend have been having mostly protected sex (i say mostly protected because there have been a couple times when the penis was inserted in the vagina without a condom, but there was no ejaculation). she has usually had fairly regular periods every 5 weeks or 5 weeks and a few days. now, she is 7 weeks away from her past period and we took two pregnancy tests on two different days, the most recent one being in the morning. they were first response pregnancy tests, highly sensitive and they are supposed to be 98% accurate in the second day after the missed period.. since we took both of them a full week after her missed period, they should be very accurate. both of them came back negative. she has lost a lot of weight recently, but she says most of this is after she missed her period. now she is saying that she has a bit of a tummy which i agree to, but i don't think it should have started to show this early and she's always had a bit of a tummy? to be honest, i haven't really noticed her fluctuations in weight.. she is a very small person at around 100lbs. i was just wondering if she could be pregnant, and what we should do about it? a blood test would be very hard to do without her parents finding out, since we would need a recommandation for it and to go to a special clinic, etc. without mine or her parents knowing. they keep her on a pretty tight leash so i don't really know what we should do. any advice?

(sorry for the really long post, i really appreciate you putting the time into reading all of it)