I don't see how your sexual orientation makes the least difference to whether you are monogamous or not. Unless "pansexual" is just a euphemism for sex addict.
Of course it's possible. There's no rules here, just whatever suits you! Sexuality is a fluid thing and so can be monogamy. For example, I would consider myself pansexual but am only desiring of my current partner right now. This could change at any time, but right now this is what suits us both.
No, not really.