Hullo and welcome!
Originally Posted by Bells
Another part of me says he has been doing this type of relationship a hell of a lot longer than me and knows what he can and cannot handle, so if he thinks I could fit into his life maybe there is space.
Part of me wants to say yes, he is an adult, his partners are all adults, and not your responsibility anyway. On the other hand, he may be kidding himself, with the new love interest in the picture he might be telling himself that he has more time in his life than he really does. When you are heavily attracted to someone you cut down on sleep and free-time activities to make time for that person. You mentioned him going out of his way, but on the other hand he has not mentioned anything about spreading himself too thin. Is the "going out of his way" your interpretation, or is there some actual evidence that he is neglecting some part of his life to make more time for you?
Are the other ladies in his life only involved with him right now? How much do you ideally think you would want to spend time with him on a weekly basis? Is that conceivable, taking into account everyone's existing commitments? The beginning stages of a new relationship, when both partners are highly motivated to spend more time together than apart, is really upsetting for most established partners. Even when physically apart, there's texting, IMing, phone convos etc.
I take it he lives alone. Does he have any long term plans with his other loves that you need to be aware of? Is he planning on moving in, making a legal commitment, having kids with one or more of his partners?