As a 7 year old boy who were you supposed to imagine having sex with? 7 year old girls? gross.
Sorry, buddy. But you are NORMAL.
Kids want to become adults and do all the things they think adults are doing. The grass seems greener on the adult side before they find out that we drink and use escape mechanisms to cope with adult life. When you learn about sex, you're not learning it from kids talking about having sex with each other. It's normally in that 20 something range. It is rare now days for a kid to not know about sex until they're older. That's why when I was young they had sex education in middle school (7-8 grade).