should i ask him out?

i really like this guy, lets call him sam. this year we were in english together and he would always want to sit next to me and do projects together. but theres this girl, lets name her jessica, and he would want to work with her also. jessica is super smart and tall and thin and pretty and talkative and has an okay butt and is super athletic.she told me that he has said she has a nice ass a lot which i know is something he likes. while on the other hand im semi-smart and chubby and ugly and have a really huge ass(which i think is super good and i get complimented on it a lot by guys and girls)hes never complimented me. she knows i like him but she has never said that she likes him. they are each others #1 best friend on snapchat while im struggling to keep a streak with him. weve never hung out after school but i really want to. hes the perfect guy honestly and i get so happy just sitting next to him. he knows about something i used to have with a guy last year and brings it up a lot, which is kind of weird. i heard from his ex that they broke up because he didnt pay enough attention to her, and with my insecurities i need a lot of attention in relationships. i really like him but i dont know what to do. should i ask him out or save the heartbreak?