I think that when one partner is in NRE they can very easily start taking their partner for granted in order to get what they want. Mostly, I think it's just easier not to see it because they are caught up in a whirlwind of infatuation.
Being a partner NOT in NRE... it can feel like your partner doesn't care at all about your feelings because they are not willing to make any changes at all. And speaking as someone who has been that partner... sometimes you know something mentally and intellectually, and yet something happens that hits you emotionally and you need TIME to deal with it. If your partner doesn't want to give you that time... it can put you in a panic that you are losing them, that they no longer care about your feelings enough to put you first sometimes, and that no matter what you think say or do they are going to do whatever they want damn the consequences.
As others have said, it's only been a month. Yes you WANT to move fast, but are you willing to lose your primary relationship to do that? You really need to take a step back, talk to the BF and explain that your partner needs some slow down time and back up a step. Give Rider time to think and process, and... if I say so myself... having a partner that sees your distress and dials things back and helps you work through it is IMMENSELY helpful. It makes you feel like they love you enough to listen and take care of you and help you through things. It makes it easier to not feel like you're losing everything. It makes it easier to work through things quicker. It's a gift. And like any relationship, you have to give as well-- you can't just receive.