Im seriously struggling with being the 3rd wheel around my friends how can i stop this?

my friends are spending all the time they can together but they also get some time with me...(or at least they did in 6th grade) i cant help it anymore then to ask them to hang out with me to instead of ignoring me at recess so i went to a different group of friends and started to hang out with them and whenever i ask one of the other girls if they can like sleep over they say no im hanging out with my other friend and then when one of them do come over they r texting their other friend instead of hanging out with me....please help me