Irregular periods after switching birth control

I am confused after switching my hormonal birth control methods. I was on the Depo-Provera shot for five years, and I pretty much had no periods while I was on it. I decided to switch to the pill because I was thinking that perhaps the shot contributed to my weight gain of about 100 lbs. So, I saw a doctor in my OB-GYN office who put me on Loestrin 24 FE. I began taking them in the beginning of July, right when my next Depo shot would have been due. I haven't really been back to having regular periods, though. I had spotting for a day or so in the first or second month, not during the end of the pack, though. I had maybe one or two periods since I've started, and not lasting more than a day or so. Last month my period didn't start until I had already begun the active pills again and lasted for about a day. Now this month my inactive (iron) pills began on Wednesday, and now it's Friday night/Saturday morning and still no period. I start my active pills again on Sunday. I was never regular with my periods before I began the Depo shot, and I never gave it much thought. I got my first period when I was 13, and whenever it came it was like, "Surprise!" I don't know if it was because I also have ADD and I just failed to pay attention to when they were supposed to arrive, or if they were truly irregular, and I never bothered to mark it on a calendar, despite my mother's suggestions to do so. All throughout middle and high school, I ignored my period until it showed up and didn't have a reason to care if it showed up or not because I was not sexually active in any way, shape or form. Seven years ago, I met my current boyfriend while in my senior year of high school and we began dating in December of 2003. We dated for at least a year before having sexual intercourse. For the majority of our relationship, I was on the Depo shot, and since it eliminated my periods, I hadn't a care in the world when it came to my cycle since it didn't exist and I was on the Depo. Now that I've switched to the pill, I was assuming I would be getting regular periods, but I'm not. I've taken almost 10 pregnancy tests, all negative, but I haven't taken any in a few weeks. I figured that if there was any chance of being pregnant, that chance would have been in July or August when I was first transitioning between the two birth control methods, so I figured tests taken in late September or early October would certainly be valid and I don't miss my pills. I am just confused as to why I am not getting regular periods. I am wondering if I should worry about my future ability to conceive, if I have irregular periods while I'm on the pill (which I thought usually regulates women's cycles), will I ever have regular periods? I just downloaded an APP for my phone which will help me track my period, if I ever get it.