Less work shifts

I'm super confused. When I first started my new job at a fish and chip shop a month ago I was working three shifts a week. Which was good because I'm getting under paid for my age. But then I got sick with glandular fever and my got my BF a job there to help out. We both have different roles but won't work same shift. Now I'm only working Friday night? It's the busiest night and I get paid more than the other workers because I'm older but I feel like I've done something wrong? I show up on time, I'm always happy (aside from when I was extremely sick) but still showed up dispite the fact I shouldn't have. I only make like one, rarely two mistakes. But we all make mistakes. Idk if it's bc he has enough people on or what. Confused