Husband lied about a relationship

[EllenSpark]

My husband and I have been married just over 1 year, and we've been together almost 13 years, with some breaks in our younger years.
A long time ago, we had a significant break of around 6 months but we did in fact continue to speak and see each other, but would tell each other we were 'trying to move on'. During that time, my now husband denied ever seeing anybody else but I told him I'd been dating others. We got back together and the rest has been history. However, I had always suspected something had happened between him and my then friend, but they'd always denied it. He even accused me of 'being crazy over rumours' and made me feel like it was all in my head. Over the years it's cropped up in arguments and he would continue to deny it, tell me I'm being stupid etc.
Anyway, last week she appeared on my Facebook messenger (even though we are not FB friends) and to cut a long story short... After a bit of chatting and catching up, she ended up admitting that they did basically have a relationship but none of them wanted to tell me at the time as to not hurt me. My husband has now admitted it but has conveniently has forgotten details. The other issue with this is we got back together when she returned to her home country for summer.
The reason I'm writing about this is I feel REALLY hurt by it, despite it happening so long ago, it feels raw as I've just found it. I'm also finding it hard to trust my husband now as he's lied to me for years, despite having plenty of opportunity to come clean. I furious he made out it was all in my head. I'm feeling betrayed by my 'friend'. I also feel sick to the stomach if I get intrusive thoughts about my husband with another woman. I'm also now feeling really insecure and wondering if he enjoyed her more etc. One part of me wonders if I'm second choice to her as we got back together after she left.
Am I allowed to be this upset about something that happened many years ago on a break? Perhaps I just need to get a grip and get over it. Maybe I'm more upset about the lying than the relationship itself.
I am surprised at myself actually for how much I'm letting it get me down.
Any advice or opinions on whether I'm justified being upset, and how to learn to trust my husband again?

The OP can ask whatever she wants. Some people want to know that information before getting back into a relationship with someone. There's no right or wrong in whether someone should ask or not.

And I would say it is absolutely is her business if it was her friend. I think it's extremely shitty to start seeing your exes friend and it shows he didn't really care about her feelings at the time (despite them continuing to talk).

Yes I couldn't get over the lies. And the gas lighting.

I would also question that he lied it to spare OP 's feelings. If he only stopped seeing her friend because the friend moved away, and the pair of them have kept in touch all this time I would suspect they both still have feelings for each other. By contually telling OP nothing had ever happened between them it was much easier for him to justify their keeping in touch with each other.
I suspect OP still doesn't know the full extent of their feelings for each other. Very convenient for him that he " can't remember " the details.

I don't think a relationship based on lies is a good relationship. And once the lies are discovered you can never fully trust that person again.

Thinking a bit more, it seems truly odd that this woman (who is not your friend) chose now to tell you. Why? She was comfortable being sly and whispering about you behind your back for over a decade.

Why is she telling you now?

It was abusive of your husband to gaslight you.

Please believe me when I tell you that one thing I have learned is that someone who will lie to your face (and in your case, not once but repeatedly over years) cannot be trusted in any aspect of your life.

I could never trust someone who had lied to my face over and over. I don't think you should try to do so either, you will be suppressing all your own protective instincts.

Do not listen to those who would try to minimise this. It's important, and so are you.

Two people who you trusted have made a fool of you and kept their sly secret from you, for more than a decade.

You are not the problem here.

Have they been messaging recently which is why it was showing in your FB? That seems strange to me.
I don’t think the relationship would bother me too much. It’s the repeated continued lies. I’m not sure I could get passed that.

This

Why did you drag up a thread from last year just to say ‘this’

Please !!