Feeling a mess.... what to do??

Ladies 6 weeks untill I’m due to pop, feeling really emotional atm, not sleeping, but I’ve got this horrible feel In my stomach that something bad is going to happen I.e my partner is going to finish we me for someone else I’ve told him this he said I’m being daft but I just can’t shift this feeling I’m feeling really heartbroken he hasn’t done anything but I’ve have seen flirty messages he’s sent on Facebook it’s probably only harmless fun but it’s really affected me I don’t want to bring it up because he hasn’t done anything wrong but I just can’t shift feeling like crap any advice???