Once you take your first pill, when do you think you can have sex?

I had sex with no condom 3 days before I started my period, AND 1 day after I started my period. I'm on birth control BUT I was at the end of my 1st pack I have ever took (taking the non-active pills) and I don't exactly take them at the exact same time every day but pretty close. I was wondering what's the possibility of me getting pregnant considering the circumstances, birth control doesnt take effect until the first month is up, but I'm already taking my inactive pills so that technically means the month is up doesnt it? Also, I was getting ready to start/was on my period, and I have a regular cycle so I dont think theres no way I could have been ovulating but im really worried, please help!

And Gail asks...
I'm 16 years old, and I'm on the pill. I've been on it for little over a month, and recently me and my partner have been doing it without a condom (were clean) since I've been on them for a month now. Question is, I'm not a perfect user. I take my pill within a 30 min. range, never exactly right on time, whats my chance of pregnancy?

And Hockeylover asks...
I've been on the pill for about a year now and I'm sexually active with my boyfriend. This past month I had sex with my boyfriend and the condom didn't break but may have leaked or something because my boyfriend seemed to think that something minor could have been wrong. A few days after that I forgot to take a pill until about 12 hours after the fact. Now, my pill pack is finished and it is time for me to have my withdrawal bleed which has always occurred at the same time. Today, however, I have experienced nothing but minimal spotting, which is unusual.

Also - just for future reference as I was always curious - I know that it is extremely difficult to become pregnant while on the pill as long as it is taken properly. However, if pills were forgotten or whatnot I realize that it is possible to get pregnant but I was wondering whether one would still experience the withdrawal bleed or whether this would not occur (just like a period doesn't occur if someone is pregnant). Does any blood that comes during a withdrawal bleed while on the pill signify that no pregnancy has occurred? Am I at risk?