Fiancée undecided on leaving, still having sex though and encountered a problem

Very first reddit post yay! Be gentle but honest please.

I know this sub deals with a lot of early ejaculation posts but this is a recent problem. And before our “separation”, I had no problem with it.

So a little background…

36 male (me), 30 female

We have been together 8 years, engaged for 2. We were looking to get married after she graduated this year. Well, we had a discussion after I felt she was becoming super distant. Turns out she had been thinking about leaving for over a year now. There is a lot to that discussion, but that’s a different post for a different sub.

On to the sex…

We never stopped. Actually our sex frequency increased. We’ve had sex about 6 times in the past week. No 2nd rounds due to time constraints. We have kids, so sex only happens at night when they are in bed.
Before she told me she was considering leaving, we would have sex twice a week. Sometimes only once. I always lasted long enough for her to orgasm, sometimes way longer than that but only when I was high off weed, and I have since quit smoking. Mainly due to preparing for her departure.

Now here is the problem (amongst many other things), I cannot last no more than 5 mins. As soon as I penetrate, I feel the urge to orgasm start. I can hold it back for a little but not long. Why is this? How come before I could make her orgasm and not lose steam before she does? But now I feel like a minute man. I can’t figure it out. Is it because of stress? I haven’t tried ejaculating before sex, it’s a rather recent problem. Not to mention, I have had times where I just can’t get the gears rolling for a 2nd ejaculation in the past. When we have sex, it honestly feels like it did during our first year dating. Super into each other and she gets very aroused to my touches and kisses.

I do want her to stay and I feel this is harming my chances of having that happen. Even if her reasons for wanting to leave have nothing to do with sex. I’m stumped and don’t know where to seek advice/help, so I came here. Any ideas reddit? If more info is required in your assessment, just ask and I will answer as promptly as I can.

I apologize ahead of time for the cluttered post. I feel like it’s all over the place lol. My mind is running a million mph so it’s hard to think straight. Thanks everyone!