I'm thinking of my ex catching me making out with someone
Do you want your ex to catch you doing that?
Yes, I want the whole world, especially my ex, to watch me make out with someone.
I know it can be difficult to deal with ex romantic partners, but you shouldn't try to do something that you know will upset him. Having him see you kissing a new partner would probably be very difficult for him. You should try to take his feelings into consideration.
I'm going to do it anyway.
You must realize that this will make you look petty and small. His feelings matter, even though he is now your ex.