I'M 16, HE IS 46

I'm 16 and I'm in love with my mums ex-boyfriend who is 46, he has kids older than me and we have to sneak around.
He says I'm very mature and sexy for my age, he never pressurises me into anything and sex happened when we both wanted it.
It is scary he is 18 years my senior, but does it really matter that much?