am i being unreasonable? sorry for the long post

I'm 7 weeks pregnant and my partner has invited all his friends around for drinks before the match tonight. which i don't mind at all he had nipped out to pick someone up and i had stayed back to jump in the shower. two of the girls he had invited turned up not knowing i was in. i was getting out of the shower when i overheard them bitching about my relationship saying how it wont last. so its pissed me off. i've ignored it but told my partner who was batted it off and told me not to be silly. then as im walking through the front room i clock a taxi pulling up and out gets this girl who he has also invited. knowing i cant stand her. she cracks on to him whenever i leave the room and acts like a complete bitch with me when he isnt around, but is overly nice to my face when he is there. ive gone upstairs out of the way because i want to cry but i also want to flip at the other girls for bitching. am i just being emotional or am i well within my rights to be pissed off/upset?