My advice would be to really consider if your acne is bad enough that you really want to start accutane. Before I started, I would say I had mild-severe acne; I would get the deep pimples that are impossible to pop and a lot of blackheads, but definitely not the worst case I've ever seen. The first couple of weeks on accutane my skin broke out so bad that I was embarrassed to leave the house. It can be really hard on your self esteem for the first month or two, so just make sure you're good with
I wouldn't worry too much about the timing of your period when starting birth control. If you haven't gotten your period since September then I would just start taking the pills now. As long as you're not sexually active then it doesn't really make a difference since you're not running the risk of becoming pregnant.