Relationships

I'm 18 years and my boyfriend is 25 and l love him too much,he is totally a husband material lol.So on Monday l told him that l wanted to take a break from the relationship because l need to focus with my studies and besides that l just realized that l can't focus both relationships and school.And l told him that we won't be seeing each other but can still chat through the phone.I told him that l would only want to continue with the relationship after l finish college and that is after one year 2021 then after that when l'm in University we can then continue.He asked me when l want to get married and l told him that when l'm 24 and he said he is oky with everything and even promised to wait and get married to me.But l just don't believe that he is going to wait for 6 years,is he really serious about me or what.Should l ask him to buy me a Promise Ring?Or is there any way or thing that l can ask him to do or buy besides a promise ring that can make me sure that l'm going to be with him? Coz l really love him so much....Please help guys!