My boyfriend had a passionate connection with his ex, and I feel insecure

My boyfriend has a tattoo of characters he and an old flame played who were romantically involved. They’re still friends. He says he’s over her but I can’t help feeling like I’m loving him from beneath her shadow. Doesn’t help that I realized the painting visible from his bed looks like her last time I visited. He was surprised when I pointed that out but agreed. I’m not sure how to deal with this. I know I have some insecurity issues but I’m not sure how to deal.

Everyone has a past - no one blips into existence the moment we meet them. It's impossible for someone to be faithful to you before you are in their life. Try to identify whether the issue is him, whether he is the one casting "her shadow" over the relationship, or whether it's something inside you being projected out. If he is specifically doing things to make you feel insecure - if he compares you to this old flame, texts her while you're having time together, etc. - then bring those up. He can change his current behavior to be a good boyfriend to you, but he can't change his past choices.  If everything in your current relationship is fine, but you just don't like the tattoo or the thought of her, consider working with a therapist who specializes on issues with insecurity.

If it's not his behavior that the problem - if he isn't doing or saying things to keep you in this state of feeling insecure or compared to her - then it honestly is a majorly positive sign that your boyfriend is able to remain friends with someone he dated. It takes a lot of maturity and perspective to recognize that a relationship isn't working in a sexual-romantic context, but also be able to hold space for how that person can continue to be in your life. Many people have black-or-white thinking; where someone is either their soulmate or a villain, and that kind of thinking has other implications that are not great.

Being able to say "this person gave me a lot of joy, and we had a lot of fun together, but the relationship needs to shift now, because our needs have changed, or we've learned more about ourselves and each other" is a powerful skill. If he had a lot of anger, regret, or shame about the tattoo, that might make you feel more secure, but it would actually be a red flag about his emotional maturity. So if that helps you reframe the situation, think about what a great guy this means he is!