Blurring sexual practices with partners
I have a husband of 5 years (together for 10), and a partner of four months, we started as a BDSM play-pairing and have become more deeply connected. It has been hard for all of us because it is new. My husband is mono and we were monogamous until a couple of years ago and my partner has never been a secondary.
The thing that is surprising me is that my husband, while finding things very difficult, is also changing in positive ways directly because of my partner and I don't know how to deal with it.
The sex was rather poor with my husband. Before we opened up we managed to improve things a lot, but since I have been with my partner things have been drastically better. He is aroused more often, initiates more often, experiments more, tells me I am sexy more. It is all fantastic! And genuine, I feel very lucky. But, some things he gets from my partner and I don't know if that is ok or not. It feels like I am blurring the lines between them and that seems a bit weird. For example, my partner is helping me with personal training. I do the exercises by myself, but I do them naked for fun. My husband knows this and today he told me he likes to think of me doing them. But for me, this is something I do "with" my partner. Likewise, my partner got me into masturbating using clothespins on my nipples. As part of the open communication with my husband this was one of the examples I gave about the sort of things my partner gets me to do. Now my husband seems to like the idea.
I feel like it is a betrayal of my partner doing things with my husband. Is this stupid? Am I over-analysing things? Should I just be grateful that the relationship with my partner has had a positive impact? It has been very challenging building an open relationship, but I was expecting challenges. I was not expecting these developments and I was unprepared for them.