For thinking my wife is cheating

She started going to the gym a year ago and it was only a few times a week. She got a personal trainer she sees him 1 time a week. Within the last 4-5 months she is going almost every day sometimes 2 times a day. Once in the morning and once at night. She has started doing things in bed that she has never done before and Talking about sex in ways she has never done before. Very defensive when I talk about how much time she spends at the gym. My gut is tell me something is going on, I let her do whatever she wants when she wants don’t question her but it has me worried.

Edit: The sex is not happening more than previously still once a week maybe. Within the past few months things have changed when we do have sex. Update: working 2 jobs because got into debt with Covid, The personal trainer contract was a year contract which I did not know when signing up. she told me she could try it for a month or two and see if it was affordable It is definitely not affordable but she signed the year contract. I work two physically demanding jobs so I stay in shape through working and with kids and sports I don’t have time for the gym. My life is Work, Family, Sports(Kids)