Of course a male doctor would tell you to have more sex!!! Kidding....
I had this problem after delivering my first daughter. Her birth story sounds just like your son's. The pain lasted for nearly two years. It hurt to have sex, it hurt to poop, it hurt to walk sometimes. My doctors always blew it off. One even sent me a gastrointernologist to have just short of a colonoscopy. Now try that with this kind of pain. I was absolutely miserable. I've been where you're at. We moved and decided it was time for a second baby. I think we had sex maybe five times in that time between delivering the first and conceiving the second. When I went to meet with a new OBGYN to have a check up before trying to get pregnant I told her about the pain. She actually took me seriously and got her medical books out. My scar tissue had not healed properly. She told me to treat it she could 1) surgically re-cut my tear 2) hydrocortizone injections in scar tissue or 3) some type of electro shock thing. SCARY!!! Luckily for me I also learned at that visit that I was already pregnant. And that I couldn't be treated while pregnant.
She made a plan of action for the delivery. In delivery, she left my daughter's head in my birth canal a little longer to stretch out the scar tissue. I tore again (and again during my third delivery) but she took a long time and was very careful while stitching me up. I healed so quickly after that birth. It was amazing the difference. Funny, my husband was happier after I healed too. Imagine that!
So go back to your doctor or another doctor. If you are in pain, don't let them blow you off. Find someone who will take you seriously. If you cannot find a doctor, call a midwifery. I delivered my third daughter at one and the midwives seemed so much more in tune to my needs that any OBGYN I used. They may be able to refer you to an OBGYN who will take you seriously and help you.
I hope the doctor gives you better treatment options than mine did. Trust your instincts when taking advice from the doctors. Good luck to you. About the sex, I did what the poster below said about the hot bath and wine, etc.
You can email me if you want to chat about it. Clearly, I don't mind talking about it. ____@____.com