Do you have a regular doctor you can go to? Have you ever seen a urologist for the chordee?
(FYI - here's an article on it. You have it, you should know what it is - https://www.webmd.com/men/guide/chordee-repair-treatment)
You say discoloration - what color is it? Is it really red? Losing color? Turning darker? Blue?
I think if you have a regular urologist or doctor, give them a call. Tell them exactly what's going on and describe the coloring. If not, go to an urgent care clinic. If that's not available, then an ER.
I don't think it's a true emergency unless it seems like blood flow can't get to your penis, or it's swelling, but if you have no other options, then that's where you go.
You mention the depersonalization. Are you in therapy or anything? If not, that's a must, but that can come after.
I don't know what's going on, it sounds like you've had some pain issues there before and so it may be time to see a urologist to at least get a current diagnosis if there's anything that looks wrong. But mostly I'm confused about why you think having the woman on top is more strenuous? And why you did most of the "work." Now, I have a problem here with my wife, who I married late in life and who never really learned how to do different positions, but woman on top is the easiest way to have sex assuming the woman is strong enough and experienced enough to know how to move properly. And in that position, she should be in control and doing at least half of the work. If you're both working together, it goes more smoothly than if you are with someone who just doesn't move much, it does make it harder on you, but not on that part of your body, it's just harder on the back and the hips and the legs. In that position, she is able to really control how deep inside you go and again, if she doesn't know how to do this, practice. I never had any problem with this position except with my wife because she's just not very coordinated and wasn't young anymore, but I'm assuming you and your partner are a lot younger so again, this should be a much less stressful position, not more. So I'd ask, did something go wrong here?
Another few days on, no increase in discoloration or pain but it feels a little disconnected but not like numb. The shape of it has changed slightly which is very little worrying, like slight "puffing up" at the base, followed by thinning out. Like before I could still sort of get hard but once again going off a more recent post the damn lansoprazole also added a bit to the ED, I think it's just healing. The people on the 111 call suggested I go to a and e for the 'acidity' reaction to the lansoprazole which was a very rare (0.1 percent) side effect, same as ED to. I think I'll be okay.