Suspicious behavior - " We have sex once a month if I'm lucky "

I have been with my wife for 8 years and married for 1 year.
Thing where good and we where trying for a baby. Then one day that all changed when she said she didn't want a baby at the moment as she didn't feel right in herself. I accepted this and was supportive In her decision.

Weeks later things took a drastic turn and suddenly are whole relationship was in the balance. It turned out she wasn't happy and it was because of me! Well I was shocked and in disbelief as I'd done nothing but love her and support her.

We managed to talk through it and then she decided it wasn't me that was the problem and that it was her. She then started to have councilling and started anti depressants. Things got better.
Then her behaviour and it got very shady.

Hiding her phone when I walked into the room, she was glued to her phone 24/7. She went out a lot with people she had never been out with before. She was angry towards me for no reason and all affection stopped.

I did the unthinkable and looked at her phone, there was a sexual message from a work friend on there. I confronted her and she said it was nothing. I asked to see her phone and she refused to let me see it on the grounds it had things on there she didn't want me to see.

Since then things have been up and down. We have sex once a month if I'm lucky and the last time we had sex she had a completely shaved vagina, which I thought was strange as she had never been bothered before unless she knew we were having sex (we plan when we are having sex, not good I know).

Basically I pretty sure she is cheating although she has denied it when I have asked. Her behaviour is not that of someone who is happy and in love (with me). Should I be worried or am I over thinking it?