Extra long period now with blood clots?

I got my period 1st of May and all was normal until the 5th, when I started having spotting. There was only just too much for a liner, so I had to keep wearing pads. Around the 15-17th it was light, before spotting again. The spotting went on till the 10th June, when it started to get heavy. I mean, really heavy. I've been having to change my pad during like, every class, and I keep waking up with my pj pants soaked. My dad and grandparents wanted to take me to the doctor, but my mum insisted it was just a little irregular like hers were when she was my age (I'm 14). She put me on some medicine 2 weeks ago that the doctor gave her to ease periods, but they didn't work. she also told me that because my anti-depressants have been changed that may be messing with my period. After 3 mornings in a row of washing my pjs, she finally decided to take me to the doctor.Since I started getting heavy I've been having blood clots. They are quite big blobs. I would really like to know what may be wrong with me, so if you have any websites with some info that would be a great help!