Can I save my relationship, even though I'm pregnant by my boyfriend's father?

I met my boyfriend in college (I'm from the UK so I think that's highschool in America?), I was 17 and 3/4, my boyfriend was 19 and 1/2.
We were in love immediately and we've been together for 7 years. I love him with all my heart, I really do.
I was a virgin when we met and to his knowledge I've only "been with" him, which by the title you can guess isn't the truth...
It all started in lockdown: Me and my boyfriend were suffering financially, we cancelled our wedding, I wasn't really working... And his father (who is divorced from his mother) helped us, he was always a nice guy but he became really friendly with us, saying that he wanted to be more involved in our lives.
When we could finally be in the house together we had a drink to celebrate, my boyfriend decided to go to bed around 11pm and about an hour later his father started tickling me. I played along because I thought it was innocent, then he started wrestling with me and holding me down. I said that I wasn't really comfortable and his response was to kiss me... My boyfriend had been having "issues performing" because of stress and anxiety during lockdown and between that and being held down I couldn't help myself.
I love my boyfriend, I lost my virginity to him, I want to marry him and bare his children and be with him forever, I told his father that what happened wouldn't happen again but me and my boyfriend were always safe, that night I wasn't, when I was "late" I started worrying.
Then I did a test, positive, then another, positive, then a third...
I feel terrible. I feel terrible because I love my boyfriend but I knew from the dates and how far along it was that the baby isn't his (like I said he had "issues performing") and I haven't told my boyfriend that I'm pregnant for exactly that reason. If he figures out how far along I am he'll know it's not his.
What do I do? I'm wracked with guilt and I can't think of anything else, it was a terrible mistake and I can't hide it forever... Please help me.
Updates
+1 y
Would it be cowardly to tell him over text?
Updates
+1 y
How do I delete this post? I'm fairly new...
Can I save my relationship, even though I'm pregnant by my boyfriend's father?
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