Oh Isabella your story sounds very much like mine... XH fell for best mates wife, was texting her all day every day, first thing in morning, last thing at night, then started to criticize everything that I did. He walked out with no warning whatsoever, came back for 6 weeks because I begged him to, made me feel like everything was going to be ok, then left again.
I took it all on board, how it was all my fault and how I needed to change! When in reality, it was nothing that I had done, he had just fallen for her.
Sorry My slight derailment there, but I know exactly what Isabella is going through. 
My It is hard, it is so very hard. You wonder how you can carry on, how you can live without him. But you do and you can. Just be kind to yourself, tiny steps, one thing at a time. Set yourself a small goal each day. Try and keep yourself busy.
I had to carry on working as I am self employed and had a £700 mortgage to pay on my own, so if I didn't bring any money in I was stuffed. So I had to keep on putting one foot in front of the other and going to work and getting DD ready for preschool and so on and so on and so on.
I cried so many tears I didn't think I would ever stop. But I did. It takes time, just so much time to come to terms with everything. Counselling will help a lot, so does talking to people. Are you talking to friends or family?