My daughter keeps throwing temper tantrums and wetting her pants i think it may be on purpose?

My daughter is 4 and im not sure how to deal with her anymore, never had this problem with my son. She is very sweet sometimes and other times she will just throw temper tantrums and throw her self on the floor for stupid little things. I figured it was out of attention so i just ignore her as does her school when she does it. But that is not working i also have tried wiping her when she does it and that just makes her even do it more so. Also she will go on spouts where she doesn't use the potty and will purposely pee her pants. She is fully potty trained and will do good for like a month, then next thing you know she will just be standing there and peee, even if you ask her if she has to go she will say no and 2 secs later pee all over the floor sometimes. I have tried giving her rewards for going and wiping her sometimes if she does pee her pants or taking something away from her but nothing works for to long. I am at my wits end between the temper tantrums and the peeing and dont know what to do. So please mothers with kids of girls that are around 4 please help and tell me this is just a phase and it will p. I cant even take her into a store because im afraid she will throw a temper tantrum, and embar me.