How do I know if he's cheating??

So I been with my husband for 3 years. We have 2 kids and I'm pregnant now. But recently, he started taking more care of himself. (It's not a bad thing) except the fact that he's spending a lot of money on taking care of himself. Haircut every 6 weeks new clothes,new shoes new phone. Also he's been coming home late from work and when I call he turns off his phone no big deal except tonight I needed picked up from my parents house and I tried to call his phone well he turned it off so instead of him driving the 25 mins home to find out I wasn't there. I called his work after they closed. I talk to him on the phone he sounded pissed but whatever. Then he called me on his cell and asked why I called work and then when I went to answer him he hung up. I'm not usually the jealous type and he's not usually the type to hang up. Like I don't go through his phone he don't go through mine but I need help...