contemplating on birth control or withdrawal

I'm starting nursing school and don't want any "mistakes" during this time. Me and my husband have been using the withdrawal method for 4 years successfully. I went to obgyn and was prescribed birth control. However I'm a little hesitant on taking it now. If withdrawal has worked this long it should continue to work right? I just wanted to be extra safe. And for whatever reason my husband is upset about me taking bc. I'm also scared about all the side effects of bc and what happens when I do want to start ttc and I can't because I was on the pill? It may take longer to ttc