potty training?

daughter is a few days from being 20 months old. we were introducing her to the potty while she was still in diapers and it got to the point that she was mostly going on the potty chair on the toilet. She would say potty and run to the bathroom or say potty and we would pick her up and take her. she still had accidents but would tell us right away with barely anything in her diaper. it started to feel like such a waste of diapers and with another on the way financially it didn't seem possible to keep up with her pace of barely used diapers. so we decided to switch to undies. It went really well for the first few days just like with diapers though the accidents were harder to deal with than i thought they would be. we wouls praise her for doing well and would act stern when she went in her pants. Then she stopped telling us when she had to go and would start refusing to go to the potty when we tried to pick her up to take her or run from us when we said "ok lets go potty." I realize now it was probably too much pressure with the negativity when she made a mess but to be fair i tried to be understanding when it was clear she was trying to make it to the toilet. But now i don't know what to do. we only started undies because she was telling us she had to go. I've relaxed a lot and am not being negative to her about accidents but now i feel like i need advice. I don't want to put her back in diapers (she really didn't like having to lay down to put them on and it's just so expensive) but this is also so much work to have to clean up the messes and with another one only 5 weeks away I'm not sure I'm going to be able to keep up with it...