Have you thought about the possibility of your butt bruising? That is a very real possibillity. While many do not normally bruise from a hand spanking, some do. The chance of a newbie bruising is definitely increased. Bottoms not conditioned to being spanked are much more likely to bruise. While I do not facts or studies to back up what I say, I know it to be true from experience. And as a spanker, I can tell you that I never know if a girl is going to bruise until bruising starts to appear. Then it can be much worse a few hours later.
I have been where you are at now, only I was on the giving end. That made it more difficult for my wife to find out I was spanking women and she never found out. I say I was where you are at because I always felt I could never talk about the need with her. She did not understand the difference between a few light spanks before sexual play and real butt burning spankings.
I feel you really need to evaluate your relationship before moving forward. Ask yourself if losing your boyfriend is something you are willing to risk. Then ask yourself if you think you could ever be happy in a relationship when spanking cannot be a part of your life. My wife passed away 15 years ago. I loved her dearly but if I ever planned on getting married again, I would not be looking anywhere in the vanilla world unless she knew and was OK with me meeting the spanking need elsewhere.