There are two issues here which are essentially related to the same thing but which actually need to be separated from each other.
The first is what is in the best interests of the children in terms of the relationship they have with both of their parents. Far too often the children are told how things will be and have no say in the matter, and this is when you end up with posts along the lines of eighteen year olds still feeling they need to rigidly stick to their EOW contact with one parent or the other and never feel they can deviate from it. Where possible I would avoid going to court to set out a contact schedule, because once the courts become involved it will be very difficult to change that arrangement in future, and trust me what is right now may not be by the time the DC go to secondary.
It is very easy for women here to state that 50/50 is wrong, but those statements are generally based on the idea that the woman will be the primary carer, and that the children will predominantly live with them. But I fail to see how it is in the children's best interests to reduce their relationship with one parent in favour of another, children have the right to an equal relationship with both parents, it's just a matter of how that is worked out. Of course not all children have that, but where possible the children should be able to see their parents equally, it's just a matter of working out how.
If the children are disrupted by alternate nights, then you need to speak to your ex along the lines of finding an arrangement which works best for the DC. When me and my ex split ds stayed with each of us for two consecutive nights during the week and EOW, so it was 50/50 in the true sense of the word. Although if XH goes away for business etc then obviously DS stayed with me. Since then things have changed somewhat and DS has chosen to spend more nights with me during the week, however this arrangement is still flexible on the basis that if he wants to stay at his dad's, then that arrangement is made on the morning he wants to stay there. My EXH wanted to change the arrangement to have ds stay at each of ours for a week at a time, but DS wouldn't even entertain the idea, and said he would stay with me during the week then. But he is thirteen and old enough to make those decisions. All of these things need to be done with the best interests of the children in mind. All too often you hear of parents telling their children how much they will miss them etc when they're not with them, and that adds additional pressure to the children to spend more time with one parent than the other, for instance. Also, if the children are finding alternate nights disruptive you could perhaps go to family mediation to talk about how the children would feel in terms of staying at each parent's. Mediation is a far better option than court, but would give the children an independent voice as well without the parents having any influence.
In terms of your own feelings, reality is that no parent wants to give up their children to someone else for half of the time, with new partners, potential half and step siblings and a life which you are not a part of. When me and EXH split I was a sahm, and since then I am still looking for work, so giving up my ds for half of the time was incredibly hard for me. And even now I find being in the house alone at night hard. But I also know that I am doing it because the idea of ds not having a relationship with his dad and the sadness that would bring to him unthinkable. And as time passes you do find ways to fill the time when the DC aren't with you.
Ultimately while it is hard, those who say you need to find a way to fill that time and to learn to enjoy the child free time are right to an extent. that doesn't mean you don't deserve sympathy for the way things have turned out, but this is how it is now, and it wouldn't be in your children's interests to change it just because you didn't want to not see them iyswim. And in time you will hopefully meet other partners, build a new life for yourself, and your children will always still be a part of that. And in time your children will grow up and leave home, and you will need to fill your life then.
Find something you enjoy, start with smaller things, watching whatever you want, having whatever you want for dinner, enabling yourself to go out if you want to, even if it's just to a coffee shop. And build on that. It does get easier, I promise.