No, swallowing your husbands semen is not going to harm the baby. I'm assuming you are worried about passing herpes onto the baby through this event. This is impossible. The risk of transmission to the infant from you is during delivery (if you carry this virus on your genitals).
Can the fact that you had unprotected sex 3 days ago mean you might be pregnant? Yes if you were ovulating at that time. However, you were not having unprotected sex then since you are on birth control (I'm assuming oral contraceptives). If you have been taking these accurately, they are very effective at preventing pregnancy.
In other words, these symptoms have nothing to do with pregnancy.
There can be other medical reasons for bleeding that have nothing to do with menstruation. Some of them can be serious. If the bleeding is significant or continues, it would be a good idea to get this checked out medically,
I live in the hot, humid south and one summer had a fungal infection under one breast. The creams did clear it up although it took several weeks. The sprays helped but my goodness, they burned like heck for about 15 seconds after I put them on; thus since you're talking about a sensitive area, I'd suggest the creams instead.
Oral contraceptives work by suppressing ovulation. IF you started taking these on your first day of your menstrual period, then you should be covered against pregnancy.
IF you start them somewhere in the middle of your cycle, the recommendation is to use some form of back up birth control (i.e., condoms for example) for at least the first 7 days just to make certain ovulation has not taken place already.
Have you considered some of the topical creams that are available over the counter for issues such as athletes foot/jock itch (which are also skin fungal infections)? They work but may take a while to do so. There are also sprays available but they tend to burn like the dickens when first used.
Keep in mind that just because your husband does not have symptoms of herpes does not mean you are not infected with this virus.
However, I would suspect that because you have had surgery in that area that required stitches that when aroused (and yes, there is blood flow to that area that causes swelling) any scar tissue may be the cause of your pain and the menopause may explain, in part the itching (i.e., dryness).
The relief from the pain with an orgasm would then be explained by this arousal business.
I suppose a good treatment would be "take two orgasms and call me in the morning" to get over the pain. Not too bad, huh?
Spotting before a period isn't unusual and it's likely freaking you out because you have been so normal before. Don't worry about it.
And by the way, the issue with grapefruit and birth control pills is not that they block the absorption of hormones but rather the opposite; they tend to block a substance in the GI tract so MORE, not less of these hormones can be absorbed into the blood stream, causing increased side effects of some medications.