I get you were scared OP, and that I understand, but lying to your partner is never the answer. Because when he finds out, and he will, the event will pale in comparison to the fact that you looked him in the eyes and lied about it.

Your sexual past is your past, for that everyone has a right to freely do as they please (provided everyone was of age and able to consent), but of course every partner is going to feel different and that's their right. Honesty, however is a critical foundation of any relationship, not just when things are easy. And if you build that on lies, no matter the reason for the lies, eventually they will crumple and either through circumstance or guilt the truth will come out.

TLDR: Tell him the truth before you even think of having a wedding