Should I try hungry baby milk?

I am debating whether to change my baby's milk to hungrier baby milk. He is nearly 12 weeks old and doesn't seem to be going any longer between feeds - especially at night. He is still waking up every 3 hours and sometimes drinking 6/7 oz. I am feeding him every 3 hours during the day also. I have many friends with babies the same age who are sleeping for long periods during the night and am wondering why mine doesn't seem to be going longer between feeds. I am debating giving him hungrier baby milk to try and satisfy his appetite. I am wondering if I can just give him the hungrier milk at t evening feed or is it a bad idea to mix the formulas. Also worried it may give him but of a dodgy stomach.