A well-known side effect is weight gain and I’m sincerely hoping that isnt why he’s trying to prevent you from taking it. :/ protect yourself. No BC is 100% but having multiple forms is way better odds for you to not get pregnant. A vasectomy might be a helpful addition to this scenario.
Go on it. Unless you’re trying to have a baby, there’s no reason your boyfriend should have a problem with you being on birth control. Especially since it’s your body at the end of the day and he doesn’t get a say in what you choose to do with it. I’d be really curious to know what reason(s) he has to be against it? Have you asked?