negative tests but I have symptoms

Please help. My husband and I had sex on Valentine's Day and 4 days later I had some spotting and then started my period 4 days after spotting (a week late at this point). My period symptoms were different this time but it did last the same length of time. On the last day I had such severe cramping I could hardly stand up (not normal for me) a few days later I started to have nausea and severe indigestion. The severe cramping came back about a week later so I went to my gyno and got a negative urine and blood pregnancy test so they sent me for an ultrasound to see if I had an ovarian cyst which I did not. I would have been about 2 weeks at this point. Over the next 3 weeks my symptoms have stayed consistent and I've gained 6 lbs despite being on a diet. I've been on the diet for 6 months and had lost 20 lbs in the first 3 months and have stayed at the same weight until the last 2 weeks where I've gained the 6 lbs. My stomach looks more round and bloated and I've had stomach pains for a few weeks and I'm now 3 days late for my period. I took another test this morning and it was also negative. I have a yearly check up on Monday with my gyno but was just wondering if it's even possible for me to be pregnant with the timeline I've given. I'd be about 5 weeks.