You are only a bit older than me, and I’ve had some similar issues a few years back. Things do change in our bodies and in our minds, those things you have to roll with. 20 years ago when I started this I had a memorable hour long session with a popular EE girl who insisted on getting 3 shots out of me in an hour, and I still knocked one out after she left because the memory was so hot! On the other hand, my orgasms now are way stronger, even if it takes a while longer to get to the finish. For me the inability to finish occasionally led to more pressure to finish, which then became a vicious circle. In my case some meds I was taking were also likely a contributor (SSRI). (So look at your meds and see if there are any culprits, and talk to your MD). That led to a worry about not being able to finish, which then sabotaged the whole thing.
What helped was a few things.
1. when planning an SP visit, abstain from any activity for several days.
2. Plan a visit where you will have sufficient time, so the clock is not a source of pressure. This includes planning the appointment time so you don’t have the pressure to rush back to work/ home immediately after.
3. Avoid alcohol the day of.
4. Don’t hold off too long, and miss the golden moment, you might not get it back. You may try to avoid cumming too soon, but that is preferable to not at all.
5. If you are having trouble finishing, stop what you are doing, and switch to something that is not focused on your orgasm for a bit. Eg kissing, oral on her etc. I find this has allowed me to get back on track by “starting over” with foreplay.
6. Take the pressure off. Realize that even if you don’t cum, it’s still fucking awesome to have some naked fun with a hot girl. Just by relieving yourself of that pressure you may find it easier to finish.
Basically go with the flow. Be less “goal directed” in bed. Cum quick and spent the rest of the session cuddling, making out, massage etc. Do this for a few sessions. Going at it hard and fast is pretty hot sometimes, especially if your partner is into it too. This will let you get a few “wins” under your belt and then worry less, the worry and lack of confidence that you will be able to cum and pressure to finish is deadly.
The blue pill isn’t going to make you cum more readily, but may make it less likely for the worry of taking too long leading to loss of erection (pressure to cum so far is the only thing to give me trouble with staying up). Tho if it’s causing distracting side effects, it may be counterproductive. Maybe other ED meds will be better tolerated.
There may, like you speculate, a component of desensitization, but some of this can be undone by focusing on the pleasure of more “vanilla” activity. Get back into more conventional porn, and take time enjoying that. That is easier to do with less pressure on yourself to perform.