Is my mare in foal?

Can anyone help i bought my mare in july this year she was running with a stallion from febuary till july the 10th.I got the vet out 2 weeks ago who scanned her and said yes she was in foal and took bloods to be sure.My vet then phoned me 5 days later to say the results came back negative.But my mare has not come into season at all since i have had her now today i have noticed slight swelling around her teats (bagging up) only slightly she has become very affectionate please can anyone help