SPOKE TO SOON ON THE POTTY TRAIING!!!

So my son Matthew did wonderful the last 3 days of wanting to go potty in the toilet. I spoke to soon saying it seems to easy to potty train i take that all back. Today is a different story we both have had one bad day. He is now refusing to go in the potty he has gone potty in his pull up all day only a couple time in the toilet. I'm a little frustrated ,but i have to hold it in so he doesn't get discouraged i've been reading the books and just need to keep him motivated this is really hard.