I would get a second opinion. I had painful intercourse for about a year after giving birth, but I had two episotmoies and a major rip that went up into my anus, so there was an obvious reason for that. With healing, and liberal use of KY Jelly, it did get better.
I also have heavy periods, and they are caused by a fibroid. Is that heavy a period your normal period, or not? There could be something that is causing that. You can also lubricate the tampon prior to insertion, if you use one without an applicator, like OB. I use the OB ultra for the best protection during my heavy flow.
Does it only hurt as you remove the tampon, or when it gets full?
Good luck, and hope this misery is over soon for you.