Waiting and Worrying - Am I Pregnant?

After reading website after website trying to figure out if I might be pregnant or if I'm simply stressing, your website seems the best as far as genuine concern and good advice, so I'm hoping you can help.

I started birth control about a year ago, and before that my periods were regular -- I started every 4 weeks on Sunday, just like a clock. My boyfriend and I started having sex so, to be smart, I started birth control pills. For the first few months I expected my periods to be a little off due to the pill, so we used a condom. A few months after being on the pill, I began having spotting in the 3rd week, and my period the 4th week (with the inactive pills). This hasn't really stopped, although I just assumed it was normal and that it might take a year or so to get my regular period back (I was also working a lot, was stressed, etc so I just figured it threw off my period a little, but since it was only spotting, I was okay)

Anyway, my last period.... I started spotting the week of April 24-30 (light spotting, barely anything although some months it'd be heavier and I'd need a liner at times) and then I had my period the following week, May 1-7. My boyfriend was in town and we had sex Sunday morning the 8th (we didn't use a condom but I am on the pill), but I was a little bit late taking my pill that day (I always remember to take it first thing in the morning, around 8 a.m.). However, I took it around 3pm when I got back to my house. Then I went to see him this past weekend and we had sex on the 21st (no condom). I was a few hours late taking my pill on the 22nd, but I took it around 1pm.

Now normally I would start a light spotting this week, because I'm in my 3rd week of pills, but so far nothing. I am due to have my period next week but am getting nervous that I might be pregant. My breasts were extremely tender a few weeks ago, but lately have felt fine, although I have slight cramping and pain where my ovaries are, which isn't normal, although again I'm super-stressed about the risk of being pregnant. I also was on antibiotics for 3 weeks last month and don't know if that could have affected my chances of getting pregant or my spotting. Lately I don't know what to think, sometimes I'm sure I'm not pregant and other times it makes me so sick, I wonder if I am...

I'm wondering if there is a chance I could be pregant -- until I started researching it lately (wondering if I could be pregant) I didn't realize it may be abnormal for me to still be spotting a year after starting birth control. Does spotting/light periods mean that my birth control isn't effective? If I took it late the two days I had sex this month mean I increased my chances? HELP!!! I'm making myself sick worrying about this, but since I'm not technically due to have my period until next week, I don't think a pregancy test would work yet so I'm wondering, can you help me figure out if I could be pregant? I used to always be able to calculate when I would ovulate and get my period, but lately I just feel like everything is thrown off... can you help? :

-erica