I get the sense from reading this thread and other things you've posted on the forum that you are considering secondary relationships with women not because you want and enjoy that kind of relationship but because you feel, deep down, it's the best you can get. I believe you would ultimately be miserable as a secondary. (Just my opinion, I could be wildly wrong.)
What you really want is a committed primary relationship, living together, building a life together. Perhaps that relationship is poly or open, or perhaps not. That's not important in this context.
If being in a secondary relationship makes you feel shitty, unloveable, and generally not as good, don't enter into a secondary relationship. (Kind of the reverse of CielduMatin's advice.) You're not doing yourself any favors nor are you doing a solid to potential secondary partners.
Value yourself enough to go for what you really, truly, want and desire most. A committed primary relationship with another woman. It may feel impossible and unachievable. That is false. Get yourself out there, push yourself to meet people. I'm introverted and a bit odd - it's not easy. Do it anyway.