I’m not sure what’s wrong

So me and my boyfriend have been together for two years. I am 20 years old. I always feel like I’m not “good” at sex or don’t know what I’m doing when we have sex. We have really only done basic positions, but I feel like he gets bored and I just feel so shitty about myself but I’m terrified to try something new. I’ve only been on top cowgirl (and I feel like I’m bad at it) and given him head and that’s really all I do on top (I have anxiety but I just can’t seem to get past it, I get so nervous I start panicking). Do you think he will leave me for that or want something else? I just feel so low and it’s really affecting my everyday life.