In a really rough spot in my relationship

I have been together with my girlfriend for 3 years we have a one year old baby boy .

Everything was good but last month she cheated on me for a week with my best friend she completely abandoned me and her son and now she comes back wanting another baby and I took her back but I’m not happy I’m super depressed and suicidal I can’t get over what she has done I don’t have any friends at all so I’m hoping someone here can help me