OP, is it only now that you are feeling uncomfortable about it? Did something prompt you to change how you feel or was it gradual? Are you feeling like you dont want to be with him? Is your marriage happy?
These days, a sexual relationship with a school student, even one over 16, means a teacher is likely to be prosecuted, gets a criminal record and won’t be able to work with children. This includes students in Yr13 who are still on roll but have ‘left’ to sit exams. Schools will also be concerned if they hear about a teacher having a relationship with an ex student soon after they leave school….as there is a high probability of potential abuse of a position of power. Even some one who used to be their teacher, but is t now, could be in a position of power to influence and exploit a young adult. Schools hearing about this would be looking into the issue and referring it on.
In the past, if a student was over 16, although frowned upon and possibly resulting in a teacher being sacked quietly, it wasn’t a criminal offence.
I suppose the question is, whether such relationships are always abusive and if it is possible for them to become happy and normal long term relationships/marriages. Also, is it possible to genuinely be happy for 20 or 30 years, and then to reflect and decide the origins of the relationship were very suspect and have this call the previous 20/30 years of marriage into question and it’s future too. I honestly don’t know.
I have known a couple of situations about 20 years ago, where a young teacher got together with an ex student and had long term relationships. In both cases, they maintained nothing happened whilst the student was at school, but it’s difficult to know if that was true. In one case, there was a gap of about 15 years and they were together throughout the student being at uni and then lived together for about 4 years after that. They then did break up. The ex-student had basically idolised their ex-teacher, but grew up and wanted freedom, whilst the ex-teacher was actually quite controlling. In the other case, the gap was smaller - probably 6 years. They were together through uni and stayed together and got married and had kids. They are still together.
There is undoubtedly something concerning about adult teachers who want to have relationships with students or ex students who are in their teens. I’m thinking mostly about male teachers, but it could be the other way round. Why would a man in his later 20s or older want to have a relationship with a teenager who they have taught? Apart from an obvious sexual intention which could be there, what kind of a man wants a long term relationship with a young girl instead of with a grown woman? The bigger the age gap, the more unequal the situation is and the unequal the power base and risks of exploitation and abuse…..even if there are very subtle and the young girl seems totally in agreement. The question is whether when there’s a power imbalance if it’s possible to be genuinely consensual and equal in the relationship.
Perhaps OP is looking back and seeing that her DH used his position of power all those years ago to start the relationship, and perhaps there has been an inequality of power through the relationship or for much of it. I just speculate. Sometimes people do only realise later. I don’t know if it’s possible to go from genuinely having thought you were happy for 30 years, to realising it’s all based on and is still abusive or not really. it probably is.