Ex Bf & New Fling. Help !

So me & my ex broke up 4 months ago over things going on in our life, weve had problems because he got put in a situation. Now Ive met a new guy I like alot, weve been sexually involved & spending tons of time together. Now my ex wants to come back in the picture, making fun of this new guy & saying how I can be with him & he doesnt care & how he feels that I wouldnt have been there for him. 
Now I dont know what to do, I love my ex bf of 4 years, but I like this new guy & he treats me weel. I dont know what to do😞 any advice ladies ?!!!! Please would help me get my thoughts & emotions together.