Post menstral bleeding

Hi...I have something that has been concerning me for several days now.

I will give a few facts about me first, though.

My periods are highly irregular, in fact, they've never behaved on a sceadule. However, recently, this has gotten worse.

My last two periods have been generally light to medium in blow flow where as it used to be heavy. Afterwards I will leave behind this...brown discharge, that I always thought was just old blood, but its been going on for nearly a week now.

Sometimes it will produce a clotting of dark brown blood, and sometimes there will be some light reddish blood (like my normal period blood) mixed in.

I am also concerned in this as I have been getting this strange feeling like I am getting a mild UTI, and am wondering if this could possibly be caused by the odd bleeding.

Oh, I forgot, I am a bit sexually active and no, I am not on the pill (can not afford it), though we do use condoms. I am on the heavy side but I have been getting more active.

I don't know if anyone can help or offer a bit of advice, but if anyone can, I would be very grateful.

Gina.