I'm hoping all the expert breeders can give some insight. Had a mare at the vet for almost 2 months for AI. Cycles were horrific with both mares, hard to get them to cycle. When one of my mares was cycling she was AI'd with frozen semen. I've never used frozen semen, and she is maiden. 2 weeks later, went back for a pregnancy check, and scan showed nothing. Flash forward to today, mare has gained quite a bit of weight with no changes in feed or hay. Blanket doesnt fit any longer and shes a smaller petite mare normally. 

could it be possible that a pregnancy was missed on a scan? Maybe im just overthinking things, going to schedule a pregnancy check next month when my schedule dies down a bit

I would have waited at least 30 days to have her preg checked. 

Yes, pregnancy could have been missed at 2 weeks {14 days}. Normally, it's 16 day check or 18 days check. Believe it or not, it does make a big difference. On the other side though, your mare could be fat. I know you are feeding her good lol.

Yes, we also check at 16-18 days for a couple reasons. 14 days---twins can be missed and that can create problems, plus if checked by 18 if mare is not bred we will know where she is at for her next cycle. 14 days is awfully tight.

this is a photo of her this evening 

She does look in foal to me and YES I have heard of a missed pregnancy during a vet check.. With the way that belly looks and hanging, there could be a foal a cooking. 

When was she bred? 

Looks bred to me also---solve the dilemna, get her rechecked. Inquiring minds wanna know. LOL

She was AI'd end of may, i wanna say it was the 26 or 27th, and checked june 11. I scheduled a pregnancy check with my normal vet for December 15