Since you say that you eventually turn on and kind of enjoy it I would think that likely there just isn't enough lead up for you. It takes time to turn off all the day to day stuff that goes on in your regular life. When you're with your boyfriend for the weekend and don't have any other committments to see to it's no surprise that you're more in the mood for sex.
There seems to be this big belief that sex is supposed to be spontaneous but sometimes it works better to have it planned. That way you can do things throughout the day to get yourself in the mind space for sexy time. Do things like send messages to each other and when you get home get yourself ready as if you're going on a date (even if the plan is just to stay home) and have dinner together and talk over dinner.
I think very likely you have NRE with your new partner but I don't think you don't have any romantic connection with your husband. I think that the new realtionship has just made you more aware of what you would like from your established relationship. Also adding more people to fix a problem in your own relationship isn't a good idea.
Everything will be ok in the end. If it's not ok it's not the end.