OK, let's see if we can sort this out together. I've looked over your past posts since you joined in July to see if there is a pattern.
Bleeding started on 3rd June.
Bleeding started on 28th June.
Bleeding started on 15th July.
Bleeding started on 13th August.
I've put these dates into a ovulation calculator that aproximates that you have a 24 day cycle.
The bleeding is light to very heavy. I'm not sure how old you are but if you are young and/or very stressed this can have an impact on your periods - besides there being any underlying medical issues - so don't panic until you've seen the doctor to check this out.
You mention that you don't want to get pregnant but are having unprotected sex. If this is the case you should also discuss your contraception options with the Dr when you see him/her. Many of the types available will reduce your bleeding and make your periods more regular and also this will remove the monthly mental anguish of thinking you are pregnant without actually having prepared properly for motherhood.
You also mention that all of your pregnancy tests have been negative and you are bleeding - these two factors are pretty good indicators that you are not pregnant. I am a little worried that in light of this you are upsetting yourself thinking that you are miscarrying. There are a lot of women on this site you have miscarried and it is not something anyone wants to go through. To help you cope with this ongoing anguish I would recommend you speak to a cherished female friend who has been through pregnancy and ask for support from your Dr. If you don't want to get pregnant and you don't have stability - both financial and emotional I'd hope that you would try to be less wreckless with your body. You are bright and caring. Respect yourself first and it will be a lot easier to respect the process of motherhood. Take some time out and get clear about what you really want. This will help you plan your future properly and take away this constant anguish which must be upsetting you. I've been lost too. We understand. Just take little steps to clarify what is going on. It's time.