Need advice -should I buy a bigger/different shaped rfboard?

Hi all,
I'm a beginner surfer with a few lessons under my belt, and I just bought my first board. I'm 6'1 and 72 kg (159 lb), and the board is a 7'9 mini mal hard board. Having used it 10 times or so I think I bought the wrong one, because I'm terrible on it!
The guy who I've been surfing with has an 8' foam board, and I can catch green waves on this pretty much every time (always popping up ok, and sometimes riding along the face of the wave instead if straight down).But on my board I haven't been able to catch a single green wave properly! If I'm in what feels like the right position when paddling I pearl every time, either before popping up or right after. If I move back then the nose is too high and the wave passes under me. It's really frustrating!
So what should I do? Stick with my board til I get the hang of it, or buy a more appropriate sized board (if so, what)?
The other thing to note is that my board is a weird shape - concave bottom and hardly any rocker (see pic). Maybe that's why I'm having so much trouble with pearling?
Any thoughts or advice would be really appreciated, thanks guys.
Jay
I'm a beginner surfer with a few lessons under my belt, and I just bought my first board. I'm 6'1 and 72 kg (159 lb), and the board is a 7'9 mini mal hard board. Having used it 10 times or so I think I bought the wrong one, because I'm terrible on it!
The guy who I've been surfing with has an 8' foam board, and I can catch green waves on this pretty much every time (always popping up ok, and sometimes riding along the face of the wave instead if straight down).But on my board I haven't been able to catch a single green wave properly! If I'm in what feels like the right position when paddling I pearl every time, either before popping up or right after. If I move back then the nose is too high and the wave passes under me. It's really frustrating!
So what should I do? Stick with my board til I get the hang of it, or buy a more appropriate sized board (if so, what)?
The other thing to note is that my board is a weird shape - concave bottom and hardly any rocker (see pic). Maybe that's why I'm having so much trouble with pearling?
Any thoughts or advice would be really appreciated, thanks guys.
Jay