I had skin expanders and my reconstruction was 2 additional surgeries. after my mastectomy I had a terrible pain right under each breast it lasted months

In answer to your original question - I'm researching this subject myself now, having had bilateral mastectomies and expanders on 6 August 2018 (and no fills post-op) - I have exactly the pain you describe cutting me in half under my original bust line. This pain line is tightening, I have implant protrusion on one side and I am attributing all these symptoms to capsular contraction + the implants used were too big. I have now asked my Doctor for a 2nd opinion referral to a Plastic Surgeon, since my current Surgeon is only offering me permanent implants. Due to the implant pain I currently have, I am very dubious about permanent implants. Also I don't want implant replacement surgeries hanging over me in the future (I am 60 now, and that would mean potential surgeries in my 70's, 80's etc if I'm still around).

I'm a little confused as to your PS's decision to only fill you to 300 and then put in 450 implants. Generally it's the other way around. I was expanded to like 700-750 and got 650 implants. This is so that it has a better opportunity to "sit in the pocket" that you create with the expanders.

My advice would be to either go back to see your PS and discuss the pain with him. If he is not willing to help you figure out what is causing the pain and possibly help fix it, consider seeing another PS for a 2nd opinion.

I am a little more than 2weeks poor recconstruction. From implant and reduction /lift on good side. At my last visit on Friday i complained how my ribs hurt under the scar line. She suggest to massage the area. Will let you know how that goes!

An update:
I found a new Surgeon who basically redid everything the old Surgeon did BUT with a wider base soft implant as well as removing a lot of excess skin on one side and scar tissue. On the comfort issue, it was an improvement but didn’t resolve the overwhelming feeling of constriction around your chest. I now think that’s due to how they attach the implants to you.

This all took place in early 2020, at the height of UK Lockdown 1. I was due a “tidy-up” November 2020 but with UK COVID running amok again that didn’t happen. In the meantime I decided to not have any more surgery unless I had an explant.

How does it feel now?
It still feels like I’m wearing a tight bra. Especially when you raise yourself up such as turning over in bed - almost feels like you about to get a stitch in your side or something is about to tear. Due to the continuing radiation encapsulation I’m definitely lopsided - 1 huge breast and a much smaller one. I wear very baggy tops to hide this. I haven’t worn a bra at all; I can’t bear the thought of another band around my chest.

With hindsight …. I wouldn’t have had reconstruction. I don’t think I was a suitable candidate as a wind musician. Also very large natural breasts were never going to shrink to an acceptable implant size as the surgeons match implant bases to what you naturally had - a fact none of them (in my experience) tell you in advance!