i'm twenty-one and never been engaged. sure i'm with the man i'm going to marry right now, but we're not engaged yet; he prefers to take things slow.
when i was seventeen, i was dating a "man" that i swore i'd marry. things were good in the beginning when we only saw each other every other day or so...but when we started spending more time together and staying together, i saw that he was really a piece of shit. he still wanted to get married, but i learned to hate him. i left him at eighteen, almost a year after we had begun dating.
my point being: you mentioned seeing each other every week, so i'm assuming you don't spend time together on a daily basis and you probably haven't spent days/nights at a time with each other. at sixteen, your feelings are very real, but there's more to being engaged and married than feeling happy when you're around that person. upon staying with him, you may realize that he is not in fact the one...as i realized with the first one. i've spent many nights and days with my current boyfriend, and though he does some things that drive me batshit, i love him for them. i love him for everything he is, and everything he is not.
i'm not here to discourage you, i just hate to see young people make the mistake i almost made. i don't really believe in a set age you need to be to get engaged, so i'm not going to say you're too young. alot of times though, people don't realize how many layers there are to their significant others, and that's what makes alot of marriages crumble.