I call my boyfriend DP on here because BF is also the abbreviation for best friend and breast feeding! People have said the same to me (he's not your dp if you don't live together) and I'm fed up with defending it so just ignore it now. In RL I call him my boyfriend and he calls me his girlfriend but I'm 40 ffs, not a girl by a long stretch. Sounds so silly being called girlfriend, partner is a more accurate description.
We are serious about each other, have been together 2 years and our families are intertwined, spending time at the weekends and holidays etc. he stays at mine 3 nights a week, but we can't live together without uprooting either his or my children from their schools or one of us having to commute with them to their current schools. Just not fair on them.
Also, much as I love him and his DCs, I don't need to be a step mum 4 days a week on top of looking after my own 3 DCs 6 days a week, so it works well to keep 2 houses. I can't see this changing in the next 8-10 years, which is faintly depressing but also strangely reassuring - I won't have to uproot my DCs or change our life style dramatically, I won't have to be reliant on a man for income or compromise on things to do with my family and home.
I have all the support of a partner, he usually comes round at lunchtime on the days he isn't with me and we talk on the phone and text every day, which is much more interaction than I ever had with XH. We talk about our problems and he helps me in any way he can, we plan for our future together and can see ourselves getting married when the DCs are all grown up, but for now, they come first and our relationship, while wonderful and important, doesn't trump their rights to feel settled and secure after the break up their respective families.
Take no notice of those who think a relationship has to have defined boundaries, we are all different and whatever works for you, your ds and your dp is all that it important.