Miscarriage issues?

I wasn't sure where to post this, but this seems the best place.
As of next month I will have been taking the Depo Provera contraceptive injection for two years, it will be my 8th injection.
It is common that after the 4th injection, 70% of women's periods stop. Mine seemed to stop some time inbetween my 6th and 7th injection. Here is the problem though. This time period clashed between me spending time with my boyfriend, (we are long distance, so spend a few weeks together every couple of months). I was a week or so late for taking my 7th injection but me and my boyfriend took other contraceptive precautions. I started putting on weight in the last few months, also assuming it was due to the injection, and so recently decided to try the Special K diet of simply switching to a low fat cereal, replacing unhealthy snacks with a low-cal biscuit bar and also started eating fat free yoghurt. After 1 week of these small changes I lost 12lbs! Shortly after the weight loss my periods have also started again on and off for 2 weeks now along with abdominal cramps.
Is it at all possible to have become pregnant for a couple of months and lost it recently?
I'd much appreciate any advice or comments, thankyou.

I have had three miscarriages. Each time though I knew that I was pregnant. Then I had major cramping, bleeding and then a loss of a mass of tissue. However my gynocologist has told me that many women have miscarriages because the embyro did not implant properly, and the only thing they experience is a much heavier period that may come late. It is not always possible. I was told that this is natures way of dealing with a pregnancy that has no chance of surviving

I have had mutiple miscarrages. I do not believe this sounds like you were pregnent at any time. It sounds like just the random crazy things that goes on in the average dqay of a womans body. With a miscarrage it is incredably painful even early on. There is no way to know for sure. A preg. test will show a false positive if this is something that just happened like today. A false positive means you were preg but you body has not had time to regulate it's hormone levels yet. You can get a positive when you are not pregnent this way. After a day or two passes the test will be negative again. I took those injections at one point in my life and hated it for that very reason. Light periods, missing periods, flooding periods, weight gain, strange cravings, so I just quit using that method. Now we use the 3 kids who has time or sanity method. I wouldn't recommend it. It's expensive. Only kidding I love my kids.