Break off the engagement. Lying and keeping secrets is a terrible foundation for a marital relationship. Disaster awaits. The marriage will fail.
That doesn’t mean you should end the relationship. It does mean you need to reboot. If you are concerned that you might be at fault for believing his deceit, you have a lot of work to do on yourself. Find a good therapist, single or couples, and look honestly at the dishonesty. The fix won’t be quick. It took years for the two of you to develop these self-destructive patterns, so it will take time to correct. But it can be done.
Step one requires breaking off the engagement. Being boyfriends is about learning how to be together. Right now, neither of you has any idea. Start over.
Good luck.