It's hard to say what your boyfriend specifically may be like. There are professional photographers who are professional and serious in their job, meaning, they don't fondle or hit on their subjects at all, and then there are the sleazy ones who are seeing this as an opportunity to get laid. I cannot tell which one is your boyfriend because I don't know him. You cannot generalize or stereotype because we are all different people. Athletes are known for sleeping around but there are some, like David Beckham, who have solid relationships with their spouses for many years, and no cheating scandals, so not everyone fits the same pattern. Then you have quiet types who look like nerds and they have mistresses up the wazoo.
If you're uncomfortable with the situation, or feel like he's purposely doing his work during days and times that you're not around, why don't you discuss this with him? Tell him it makes you uncomfortable and tell him that you feel insecure about it. Perhaps he feels uncomfortable with you around, or the models felt uncomfortable and said something. I am a hobby photographer and personally, I cannot stand people watching me or standing around while I am taking pictures, because I feel rushed and nervous, and because my specialty is wildlife photography, having someone standing around and making a sudden movement can ruin my opportunity. Perhaps the same thing applies to him. Rolling your eyes at a woman's sexy posing might ruin the moment, the look in her eyes, or she may feel she needs to cover up because you're throwing daggers in her direction.
At the same time, if he was a nude photographer when you met him, you knew what you were getting into when you started dating him. If you're a jealous woman, you should not have initiated a relationship with a man who is around a lot of women, naked women, specifically. If he is not telling you that he is doing nudes or claims they aren't nudes but then you find out on his page that they are, there is some deception going on, and that is a big reason to feel a lack of trust. If you're already starting off with a lack of trust in your relationship, I'm afraid to tell you it's only going to get worse and you should just break it off.
For what it's worth, a male acquaintance of mine is a nude portrait photographer. He paints at all crazy hours of the night in a historic home that is used as a gallery (he and his business partners are also owners of several galleries here in my city). He has a girlfriend, but he tells me she struggles with trust and they constantly break up and make up, so you're not the only one. He has begged me to pose for him and he is very charming and flirtatious. He was always sending me messages telling me I was beautiful and how much of an honor it'd be to paint me. Personally, I would not care to have my boyfriend acting this way towards other women, even if he's just using that as his "marketing scheme" to make them fall for his charm and accept being painted. He would charge people who would ask him to commission a painting, but if he chose to paint someone of his own volition, he'd do it for free. I never asked what he'd do with the proceeds should his painting sell, considering the model should probably receive some sort of compensation.
Considering my only experience with someone who deals with nudes, I'd probably be unhappy dating someone who does this for a living, and that is okay. You and I are both entitled to our feelings, there is no "wrong" or "right" here, you feel what you feel. The sea is full of fishes and while he may not be the right guy for you, he may be the right guy for someone else who is sexually open (a woman who is into threesomes or swinging), or a woman who feels all men cheat and is open to him fooling around as long as he keeps supporting her and comes home to her and to pitch in with the kids. Yes, there are plenty of women out there who feel cheating is a part of life, part of a man's biology, and turn a blind eye to it. Again, there is no wrong or right here, you either agree with that lifestyle or you don't. Best of luck.