should i leave my boyfriend of 6 years for our 2 kids

We have been together for 6 years we have a son who is 4 and a daughter who is 19months my problem is I don't no if I should leave my bf or stay for the sake of our kids I love him but I don't love him the way I used to I'm so unhappy and pretty depressed he treats our boy like dirt while he treats our girl like a princess and our son is very unhappy which has caused him to become very naughty I i have trouble controlling him me and my partner have Sat down aqn spoke about it and he has tried to change which only lasted about 2 weeks now its back to how it was except my son is now worse I have been seeing a counsellor also to try different things to get it back to normal but I've done I i can an no to make it work we have grown so far apart I just want to do what's best for myself and especially my I i want them to be happy but if I leave I don't no how they will react my kids love their dad very much an get excited when he comes home from work an I'm afraid that I i did leave it would tear hem to pieces so I don't no whether to leave or stay for the ake of my kids being able to stay in the same house as his dad please help I'm st to get really down about not knowing I i should do what's right and what's wrong.