Im sorry you have to deal with this issue... clearly its not normal outcome, or in any way psychological.
If its pushing on outwards, it means that your surgeon was trying to remove crus of penis, and he messed up things halfway, and decided to leave it like that after he wasnt able to remove it successfully. Thats the only explanation why it actually pushes on outwards during arrousal. Crus is partially dissattached as he was trying to remove it. Why he wasnt able to remove it completely, is outside of my understanding. Most srs surgeons, and urogenital surgeons who do this surgeries, do their best to completely remove all erectile tissue, including bulb of penis and crus of penis, as if there is erectile tissue left, and NOT incorporated correctly, it usually leads to problems like you have, or similar. Dr. Suporn is one of the rare surgeons who feel confident to actually retain inner erectile tissue (he removes the outer part) and incorporates it to mimic the erectile tissue in biological females. Even then there were a few patients who ended up having problems and wrote about their experience online over the years. I bet there were some more who didnt report about it online. Regardless, most patients (including myself) dont have any problems. With arrousal, you usually experience pleasant fullness, not only around clitoris, but in whole area all the way down to vaginal opening. This is pretty much how most biological females describe it. There isnt any visable change on the outside, and there isnt any obstruction directly on vaginal entrance.
I dont know why your surgeon wasnt able to remove it. Obviously there was something beyond his abilities. I wouldnt recommend you go back to him, if he wasnt able to remove it then. I dont know how many urogenital surgeons, trained in SRS you have in your country. You should probably check that. I dont think this is a case for plastic surgeons. I know many with such and similar problems go to Dr. Djordjevic in Belgrade (Belgrade center for genital reconstructive surgery). There is a section on their website "Vaginoplasty re-do" with photos of revision surgeries, - cause: erectile tissue removal.