Feeling lost and dumb

I'm 24 weeks pregnant and my child's father moved in with a new girl in another town and now they are in a relationship. I feel so dumb to be having a kid with someone who's now in a relationship with someone else. I feel people are gonna laugh at me and not understand why I'm having his kid but I was pregnant before they got together. Like I know I probably shouldn't feel this way but I do I just need some advice on what to do as far as moving on with my life and should I honestly feel dumb or not