There’s two sides to this - one will have a positive outside and the other one not so positive unfortunately.
he will only get better if he WANTS to get better. If he does, then there are lots of options , if he doesn’t then nothing will improve, the sex, his ability to get an erection and ultimately your relationship will all go south.
For those saying ‘just get some Viagra ‘ - it isn’t that easy and straight forward, also Viagra will typically only work for around 60% of men with ED.
i had ED in my early 30’s and it destroyed me. As a young , fit man, I felt inadequate, less of a man, depressed and my partner at the time game me no support, cheated on me and the relationship ended.
I wasn’t prepared to go for the rest of my life with no sex life. For the two years that I battled with ED, I lost size ( over 2’ due to atrophy) - if your partner doesn’t get NTE ( night time erections ) then he will likely also lost size , something which most men are oblivious to.
Viagra worked for me for a time, but it gave me terrible headaches and dizziness. The effects then wore off after 6 months or so. I found Cialis better ( generic name is tadalafil and is much cheaper ) - I would recommend a 5mg daily dose which he takes each morning as it lasts up to 36 hours.
cock rings are also good for keeping the blood in the penis, but he needs to be able to get an erevtion in the first place for these to work. A urologist will do a Doppler to test the blood flow in and out of the penis.
i also tried a vacuum pump and injections, but both required preparation and weren’t ‘sexy’ .
At 36 I got an implant, which is the last resort , it’s terminal and once implanted a man will never get a natural erection again. It changed my life , but it changed my life because I wanted to change my life.
it doesn’t sound like your DP is anywhere near this extreme stage yet, but if his issue is physical and not psychological then it will almost certainly get to this point at some stage in the next couple of years.
However, if he is burying his head under the carpet and doesn’t want to get help or see it as an issue then your options as a partner are limited unfortunately.
if this was a 10 year relationship and his ED has gradually gotten worse then I’d say without hesitation to support him and encourage him to get the help he clearly needs.
However, at 4.5 months I’d suggest if he thinks it will improve on its own and does nothing about it then walk away - you can’t help someone who doesn’t want help.