Am I pregnant? Two positve results, two negatives?

I had a period over 3 weeks ago but I am not completely sure, it could be four weeks. My periods have always been irregular so I don't take note of days etc. My last period (whenever it was) I bled for a few days then stopped, then a few days later I started bleeding again but only for 2/3 days. I am not on the pill and I have been having unprotrected sex with my partner so I decided to do a pregnancy test on tuesday, the result was unclear, when I first looked I presumed it was negative but then I looked closer and there was another line it was extremely faded. The next night I bought two clear blue tests, the first one I did, didn't work. I did the secnd test the following evening and this came back positive but also with an extremely faded line. The day after this I went and bought two digital clear blue tests which both came out with negative results. So I went to the chemist, when I told her aout the positive tests she was determined yu can't get a false positive result but then when I showed her the digital clear blue she told me that I should just go with that result because they are very good tests. I am so very confused, I have 'period' pains today, like I am going to come on my period. I just need advice! Help!