idek what to do

so I like men I have a boyfriend I live with I think I might like girls I just wanna try to have fun with another girl and pleasure her & her do the same to me I ain't never done nothing like it beside kiss a girl I'm kinda scared to do anything more but I get so horny and wanna fuck with her with a dildo and see how much my hand can fit in her & how deep and how much she can take and I won't the same done to me am in the only one ? I feel like I'm a huge freak and shouldn't do anything