You should focus on your marriage. There's a reason that you left your old boyfriend, and plenty of reasons you married your husband, so stick with the guy who made you happy enough to solidify your relationship.

You can fall in love with multiple people. Nothing surprising

Work on forgetting the ex. Remove him from your social media, or at least unfollow so you Don’t see him. Don’t pine about it. You love your husband, so work to feed that love. You can either control your situation or you can screw up what you’ve got by thinking about what might have been and quite easily not have either your husband or your ex. You’ll never be able to know what might have been, so there’s no point letting that ruin what you have.

Okay, so you're polyamorous. Lots of people are. It doesn't mean that you have to be practicing poly. You can be poly and stay in a committed, monogamous relationship. It'll put some strain on you at times: One partner can never be everything you want. Make sure you maintain good, solid friendships for additional support and enjoyment. If and when you decide to feel out your husband regarding poly arrangements, it should ideally happen once you two are very secure with each other. There are lots of ways to do poly, ranging from permitted one-night stands, to swinging, to having multiple committed romantic relationships. Read up on it when you want. The three most important things are: 1. Each relationship takes a lot of time and energy. Your time and energy are limited. 2. Monogamous relationships have some problems which the couple can comfortably ignore. Poly will bring those problems right out, and make them impossible to ignore. You *need* to have good conflict resolution skills. 3. Jealousy is neither a problem nor, as some would have it, an unnecessary feeling to be banished. Jealousy is a *sign*: Usually a sign of an unmet need, but also a sign of fear of losing something or someone. Rather than address the jealousy, address the problem that jealousy is pointing out. (You don't fix a "check engine" light by pulling out the dashboard light bulb.) Good luck.

I'd advise you to stick with the one you got, and hope the love for your ex passes. Good luck!

Stay faithful, you will move on eventually, and your feelings for your partner will grow stronger. Seek counselling if you need to.

It's called polyamory and there's nothing wrong with it... as long as everyone else involved is cool with the situation. If not, then time to forget about the ex and move on.