I need a lil advice please(heartbroke)?

in march i caught my fiance' sexting some dude..i think it lasted a couple months and caught them before it went to another level(i hope) but i cant get over it..it hurt bad,i feel like im not good enough or shes interested in other men...shes said shes sorry many times and got me a sweet card expressing her mistake and promise it will ever happen again..yet i still cant help thinkin they had sex which they both deny(i contacted the married fool) but supposedly they aint talked or texted since i bustin them out..i may have ended there fun but now im jus flatout insecure..what should i do? i do love her and we have a 2yr old son