My fiancé is tainted in my eye

We are getting much better and she is working really hard to show me how much she loves me. But the fact another man was her first, another man has seen her naked. Another man has put his penis inside her makes just gives me a weirrd feeling. Hell I’ve been with more women than her but it still bugs me to death. I know it’s my own insecurity, so I am beginning therapy in 3 weeks and hope it’ll work by our wedding.