Has it been cultured to know for sure that it's herpes?
It sounds like it is, but you want to make sure it's not something bacterial that needs an antibiotic. If it's been cultured, and you know it's herpes, there's no need to go back to the doctor.
Yes, you can transmit it when it's active. You should keep it covered, and if you wear contacts, you may want to wear glasses while you have the outbreak, or pay very close attention and not use that finger to place your contacts in your eyes.
I'm sorry this is happening - I've heard herpetic whitlow (herpes on the fingers) is very painful.
I did not have it cultured, however, it was coming back almost as soon as it heals. So herpetic whitlow, is that type 1 or type 2? I suppose I could Google it and should. I avoid touching things others might, I avoid touching others (handshaking, etc). It is painful and I don't think it would have cropped up this time had I not missed a few days of meds. When I first got symptoms, and went to the doctor, he said, "oh, that just a whitlow, it will go away." And it did. But then a month or so later, I had this painful blister on my finger and thought I had gotten a splinter. My then husband got a needle and began digging in the blister but it hurt a lot and I made him stop. Within a couple of hours, I had multiple blisters on my finger. That is when I went back to the doctor and this time, my husband wanted to go along (never before did he go to an appointment). The doctor said it was a "shingles type virus." So imagine me, walking around for the next year, thinking I had recurrent shingles. And then, some anonymous person contacted me via social media and told me that she got herpes from my husband (we were only married about a year or so at this point) and thought I should know since he never told her he had the virus. I told him when we first began dating that I wanted us both to have blood work for STDs and he assured me he just had blood work done and he was clean. I should have known better, I should have asked to see the results. I didn't. After we got married (it was one of those whirlwind romances) I began to find out how indiscriminate he was as far as sleeping around.
I guess the moral of my story is this: insist on blood work when you begin dating. Don't take their word for it- ask to see recent results. Some may say this is only a skin condition, but for me, its much more than that. I have to take Valtrex, daily, the rest of my life to keep this from constantly resurfacing. The virus is painful and having it makes me feel dirty. I have an autoimmune illness as it is, and I think that is why the blisters would go away and then come back within a week or so.
Whitlow could be either 1 or 2 - you can get either type on your hand. Testing is the only way to know.
I don't know how long ago you married your ex, but good blood tests weren't available until fairly recently. It may also be that your ex went in, said "I want to be tested for everything", and thought he was tested for herpes, and wasn't, since even today, most STD testing doesn't include blood tests for herpes.
He may also be a total jerk and knew it and didn't tell you, but about 90% of those that have herpes (of either type) don't know they have it, so it's possible he didn't.
The only time you're contagious is if you have an outbreak. If you have it genitally or orally, you can transmit at other times, but the skin on your hand doesn't shed like the mucous membranes of the mouth or genitals do.
You don't have to take extraordinary precautions to not touch things, either. Herpes isn't spread via surfaces and objects. The only thing I would advise is that if you dry your hands on a towel, that no one else uses that towel while it's damp. That's a mainly theoretical risk, but since it's possible, I'd not share towels.
Herpes (or any other STD) isn't a reason to feel dirty. You have a virus that upwards of 70% of the population has - either type 1, type 2, or both. It's just a virus. The reason people feel guilty is because of the mode of transmission, and because we assume others will think badly of us.
It doesn't matter if a person got herpes from having sex with one person or the 20th - all it takes is one time, and we all have different experiences in life, and experience sexuality differently. Having a virus in our body is not a moral judgement. Viruses, bacteria or whatnot just do their biological thing and reproduce and transmit - they don't care if you are the nicest person who helps little old ladies cross the street after church, or you're the worst person ever - they don't have the ability to know and determine that.
It's not always easy, but don't let yourself buy into the stigma of it all. If you wouldn't tell your best friend she was dirty for it, then don't tell yourself that. :)