Frankly, I think it's really invalidating to suggest that "true love is a rare phenomenon." I think that a lot of folks in the world would be surprised to find out that, in fact, they have never truly loved someone. I'm not even going to touch the stuff about rape...

But as for the rest of your post, I doubt that it's some matter of true love or imprinting or whatever. The meds surely complicate matters. And you said yourself that you could orgasm with your current lover at first.

It sounds to me like you had one fantasy (the idea of your first husband) that really got your motor running, and you got used to using it as your go-to. It's quite common for people to get used to orgasming in one way--through one specific type of stimulation, in one specific position, thinking of one particular fantasy, watching one particular type of porn. This becomes self-sustaining, and it becomes hard to orgasm in another way, with other fantasies, etc.

There are ways to get over this. One way is the cold turkey method: stop using that fantasy, period. When you masturbate, fantasize about something else. Sometimes, your body will eventually respond to this. You'd have to be willing to be patient and frustrated in the meantime.

Another method is to use your usual fantasy, bring yourself near orgasm, then switch to another fantasy. This can be tricky for women. You may need to switch just in the last couple of seconds, then the next time try to switch a little earlier, then a little earlier the next time, etc. A variant on this is to masturbate in your usual way / thinking about your usual fantasy, bring yourself very near orgasm, then stop; continue and bring yourself near orgasm again, then stop; repeat however many times, then switch over to a different fantasy / stimulus, and bring yourself to orgasm.

Or spend some time masturbating and daydreaming and see if you can think of another fantasy that gets your motor running even more. Or tweak your fantasy a little bit: for example, you could try imagining that you are with your current lover, but that your first husband is in the room, ideally with your main focus being on your current lover. Or imagine that you and your current lover are roleplaying that he is your first husband. Or talk to a therapist to see if you can suss out any underlying, unresolved issues that cause you to go to this fantasy.

In my experience, re-wiring your body to new types of fantasies and stimulation is a long-term project. But I suspect that it's possible for many, if not most people. If you do a Google search on how to change your fantasies, or something similar, you'll find more suggestions.