I just went off the pill also. This is my first week off and I've noticed a difference in my mood. I'm not sure if it is the fact that I'm off the pill or if it's just been a stressful week. But my emotions have been intense and unpredictable. I've also been extremely irritable.
I think that changes in the body going on or off pills is different for everyone. I know that when I start my periods again, they are going to suck. That is one of the reasons I love the pill. Before I started taking them (about 10 years ago), I had 7 day-long periods with heavy flow, cramps that would put me out of commission for 2 days, vomiting, backaches, and migraines. I'm hoping I get pregnant soon so I won't have to deal with PMS. I know that pregnancy isn't a joyride, but at least that discomfort has a purpose.
Before I started taking the pill, we used condoms only. I never got pregnant, but then again we only did that for a couple of months because I was sensitive to condoms. Nothing is 100% and getting pregnant is a risk you have to take when you do the old in and out. However, with all the methods of preventing pregnancy available, I find it hard to believe that responsible people get pregnant on accident. But it happens from time to time so be prepared for the effect of having sex.