My DD is the same age, and we are still working on it too. One thing that helps her to go is to have certain "routine" times of day that we go...first thing before getting dressed, after lunch, after nap (if I am lucky enough that she takes one), before bed. Usually not much struggle getting her to go then. It is just like mid-morning or other times when it has been awhile that I struggle to get her to go, and the sneaky times that she poops in her underwear...gross! I have noticed with both of my kids that they are more interested in going in bathrooms other than home, so for us, being out and about helps a lot. I think part of my DD's issue is that she wants to do everything herself in her way ("ME do it!!!" is what I hear all the time), but also is either not quite noticing when she needs to sometimes or is too engrossed and having fun playing to want to stop and go potty. Are you doing underwear full time or diapers some of the time? We start out with purple underwear (her favorite color), and if we wet/poop in them we have to wear the boring white underwear. Sometimes I also give her the option of wearing a pullup if we both just seem too frustrated with it for the rest of that day, then start over the next day. Potty training is NOT fun, and we clean up a lot of messes, but she won't be going to high school in diapers.
DS was close to 4 before he finally got it, then was doing it entirely himself with little to no help shortly after. Both wear pullups at night yet. I myself had nighttime accidents till age 6 or 7, so I am not worried about that yet. Don't know if this is so much advice as sympathy since mine is the same age and at about the same stage!