New position, am I wrong for feeling mislead?

I went in for my first day of training yesterday and things changed a bit. I wasn't given the opportunity to negotiate my salary, I was presented with a number that "we agreed on" (we did not, when I left the interview the final word on this was being told numerous times that it could be negotiated). Now I may have screwed up by not negotiating before/during accepting the position. Also come to find out, the schedule is actually Saturday and Sunday nights, Monday day, and Tuesday-Wednesday nights. I was also asked if I preferred Monday nights as well as "this can be changed". I am not a confrontational person, it's one of my biggest flaws, so I just stood there and said "okay". Looking back I should have said something but I'm not sure how to say something on the spot without sounding demanding or unhappy or ungrateful, or that I'm asking too much.

I'm not going to lie.. I cried on the way home, and I pretty much was emotional/tearing up ever since I got home last night. I was extremely excited about the opportunity, the money sounded so good and it's needed right now as the financial weight has been on my partner since Covid and there's been some issues/resentment because of it. But I'm not even excited to tell people anymore and I just feel sick about the whole thing now. My partner and I will be on complete opposite schedules and I was fine giving up Saturday nights because I was going to be home Monday-Friday nights and it was well worth the money. I don't want to sound ungrateful or bratty or immature, but I just felt very blindsided by the switch up on schedule. I know I didn't mis-hear the information during the interview because I literally left thinking how perfect it sounded. I'm also a full-time online student so I'm sure the stress of it all on top of school isn't helping me feel miserable.

Do I just need to suck it up and deal with being miserable and seeing my family less until I get used to it? Is it too late to question the changing of schedule and lack of salary discussion? I have to train basically every day for the next two weeks (I have two days off, one being Easter) and I'm completely in a negative mindset. Anything to help or anything you think I need to hear or can suggest, I appreciate!

Edit: Also, I understand I'm essentially the bottom of the totem pole person and I can't expect everything I want right off the bat, I just feel like my expectations were set up. The other manager is the one who I interviewed with and was offered the position through, and I feel like maybe I was told one thing and given another due to what she preferred for herself. Also.. the person who was in the position before me is stepping down to become a server, which also makes me wonder as well.

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Edit 2: Ignore my typo in the title please lol. Sorry.