More than likely all along the probem has been hemorrhoids, altho I cannot discount a fissure. Hemorrhoids are very common, it comes from straining during constipation. Constipation is where waste won't come out for a couple days or so, and it piles up and gets larger and harder, so when we strain to get it out, the vascular tissue there bulges out into a hemorrhoid. These hemorrhoids will then bleed as waste goes by, and often will get to itching and stinging like mad. Hemorrhoids come and go, fortunately, as our digestion works better. The solution to make it stop with the hurting is to put something like plain KY jelly on there in the blue and white tube at the pharmacy. Put it on after you bathe, and reapply as needed, it eases chafing. Others like to put ye olde Preparation H on their hemorrhoid area, it causes them to shrink and thus not be as vulnerable to waste passing by.
To prevent constipation, the three standard ways are: Drink extra water, and exercise regular, and eat enough fiber foods (like oat cereal, whole grain breads, dark green vegies and salads). Also, if you find you are getting constipated, take the natural Senocot laxative, and you'll get rid of all that stopped-up stuff.
If it turns out these things don't work and perhaps you do have a fissure, you would need to see a physician, but since you have no insurance, you can go to the county health department and be seen by a doc there, bring your W-2 and they'll charge according to what you make, which happens to be a very small amount no matter what you make. You can go as a walk-in and be seen the same day usually. Each free clinic has its own rules. But try the other things I suggested, and if you are still suffering, then you can go to the clinic.
As for relations with your girlfriend, hemorrhoids once healed will give you no further trouble. While you're healing, you can put the plain KY (not the flavored kinds) on there after you bathe, as I said, and it will last until next time you shower, since it's water soluble, so that will "protect" you from fluids and such. One tip: Sometimes I have to pass waste after I shower, so I'll squirt some KY on a damp tissue for the final wipe, and it stops the hurting and protects the area. They also come in little portable packets for when you're away from home.