I am going through a similar issue with my female partner. My other lover is male and she feels because he has a penis and can do things sexually for me she can not do without assistance that my sex life with him will always be more fulfilling.
This is the
very reason I am so thrilled and encouraging my wife to explore her affinity for women! Years ago, if she approached me about sharing intimacy with another woman (with or without me present) I would have thought
"That's so hawt, chicks-on-chicks!!! WOOOO!". Now that we've been married for a while, I've accepted what I can and cannot do, and want her to experience other people. I haven't had a
ton of partners in my life, but I've had many more than she, and I've gotten to experience some of the variety Mag mentioned (only from the male perspective about different women).
That said, Vera I can relate to your BF's point of view, because none of this involves another man
yet. For me, in considering and accepting opening our marriage to poly, I know I have to face that particular trust issue, (as does my wife should I become involved with another woman). What helps me is to take it to heart that just as other women can be a source of adventure for her to explore, learn from, and develop strong intimate relationships, it's really the other
people part that's fulfilling her, and nothing gender-specific. (That's not to say that you women don't bring some very wonderful gender-specific things to the table
- God bless you all for that).
I think most people, but men in particular, can dismiss bi-relations as completely non-threatening (thanks society!), but the minute another potential protector shows up, we tend to assume that our role and importance will diminish greatly. Watching our lady go through NRE can be particularly painful if we're not ready for it, because we want to be the ones that make her feel that way. Unlike with bi-relations, we have to consciously override that reaction and remind ourselves that this is
precisely why we got into this in the first place. We also have to remember that this is for
her, and ultimately for both of us in the greater scheme of things.
Remember that the ability to please and satisfy your partner is a very important cornerstone in most men's self image. We all have gifts and I know there are some things I do that are really great. There are other things where I think, "man, I wish I could call in someone to knock this part out of the park for me". Try to help him see that it's "different sex" and not "better sex" and you want and enjoy both. If he's particularly sensitive about it, I wouldn't bring up details though. The same applies to the emotional bonding - but that's a more fundamental poly issue (love as a finite resource vs. an infinite one).