Hi Quinn,

This is really a pastoral question and a medical issue, neither are areas we are experts in. We are Catholic apologists and help people understand Catholic Doctrines.  While this is doctrinal because it involves a moral issue, it's also a nuanced issue.

But let me take a stab at your question and give you some insight. 

First, I suggest you mention this in Confession. You don't need to give the priest every detail, but just basic facts. This happened:

• I did this, in order to finish in my wife.   

From what you describe, you made a successful effort to not finish outside of coitus.
From your question, we can deduce you didn't know whether you were:

• committing a sin, as well as,
• in the heat of the moment . . . able to make a clear objective decision.

so, there is gray area here regarding sufficient time to reflect and have full consent of the will.  

The Church understands the couples engage in foreplay and even "after-play" if the wife hasn't been satisfied during intercourse. So long as none of this activity is demeaning, they are done in love, as an act of self-giving this behavior is fine. So, in a sense, what you did could fall into this category. 

In addition to your priest, you should talk to your doctor. (Hidden medication) is a known cause of sexual disfunction, however the good news is it appears there are possible solutions to offset the symptoms you're experiencing or have experienced.

I'm not a doctor, so I can't give you medical advice, other than to discuss it with your doctor but a simple A.I. search asking,

"Are there offsets for sexual dysfunction caused by (hidden medication),"

will give you some information that I'm sure your doctor will have.

Look at what the A.I. says and discuss it with him or her. 

I hope this helps.

John