Ladies, how would you feel? Sorry for long post

Okay so my partner went out up to Cardiff the other weekend with his lads for one of their birthdays, obviously I didn't mind. 
When he came home he told me about a girl who was asking him to go back to hers, when he said he had a girlfriend apparently she responded saying she will never find out. I forgot to mention she was also in love island which made him feel great. 
That afternoon one of his friends finds her Instagram account and tags him in the comments of her photos and then she followed him and liked some of his photos to which he responded by screenshotting it and sending it to all his mates like proper happy and bragging. This happened again when she liked a photo. 
Now I see him liking some of her photos, baring in mind she is also a stripper and posting very provocative photos in underwear and doing ful splits etc. 
Bearing in mind I am 36 weeks pregnant and feeling more insecure and ugly than ever. How would you feel? 
Sorry for long lost