Your story could be me and lots of others. The stigma, the day-to-day fear and terror of being taunted by your classmates, feeling alone, being an outsider, etc. is ALL a side-effect of this religion. You never got over it and hid it all those years. When you hide something, you are allowing "IT" or "THEM" to have power and control over you. Simply put, you have chosen to live as a prisoner of other people's thoughts all these years due to the traumas inflicted upon you during your youth. I'm not being critical of you, but save yourself the money from having to have a therapist tell you the same thing. I'm very open about my upbringing because the vast majority of adults and sane/free thinkers totally get it at this stage that as kids, we all have very little choice in how we were being raised. When you mature and come of age, you make decisions to either keeping being what you are, or be different from what you once were. I simply tell people I was raised one of Jehovah's Witnesses and due to some problems I had with the teachings and how I was treated, for my own health and mental well-being, I just couldn't go anymore. Problem solved and I've never run across anyone who was critical of that. Actually I have people ask me more questions about the Bible after they find out. Kind of a weird witness situation that seems more natural than ever before. You will cause yourself way more grief and trauma if you keep hiding it. Instead, grow up, be open about it, it's part of you and anyone who holds you in derision over it is a bloomin' fool that isn't worth your time. You had no choice in the matter at the time, but now you do.
I must mention that I don't have a large circle of friends. I seldom ever go and visit friends anywhere, I come home from work, fix a meal, surf the net, work on my farm a bit, and my wife and I pretty much keep to ourselves. We have friends that we keep a good 100+ miles away that we are welcome to go see anytime and hang out with and in so doing, we do maintain strict control over who comes to the house. I have a couple of close-knit "worldly" contacts that know my story and they of course are allowed over anytime - I'd actually trust them to house sit for me. I'm a jack of all trades, so anyone who takes issue with my Witness past, can usually be subdued when I fix something of theirs for cheap or free and they realize, I'm not such a bad guy after all. I can see how if you're the BBQ-on-the-weekend type, and drink, watch sports with the gang, etc. then the shallow-flighty nature of that social situation could wreak havoc on your fantasy life of fun and games, but in the long term it's best to come out with it. Part of not being embarrassed or ashamed is to never outwardly show it. Growing up as a Witness, I became very good at acting - to a pathological level - but when you show no shame - it's funny but the shame actually transfers to the person who thought you should be ashamed. Then they're ashamed that they thought you should be ashamed.
I feel for you, but I've learned to cope and deal with this every day. For people who are more sensitive emotionally, being a Witness is pure torture, and I completely understand why the suicide rate is high and largely ignored by the upper brass.
I wish you well. You're in good company here.