Hello,
since you took plan B twice in a month - and they recommend that you should take it months apart - chances are that you're over reacting because hormones from the plan B, than that you're pregnant. You need to take into account that each dose of plan B basically is a high dose of the same female hormones that birth control pills contain. Since you got your period and had two negative tests, seems like plan B did its job. But that also means that you took two big doses of female hormones that cause changes like in PMS or menopause - you feel too emotional, stress to much over everything, ... etc. But I have to say, you really need to consider some other method of contraception - take birth control pills, if nothing else,
Wish you all the best,
Nicole