Feeling low about never having a relationship

Sound stupid, but I went on a party boat today for my friends 18th birthday and realised I was 7 wheeling with my friends 😭, and it was all cool like it wasn’t an issue until later in the evening we went to the top deck to watch the sun set over the harbour (btw this is in Sydney) and they all left me. I was cut but didn’t do anything cause they had involved me in the whole day they all probably just wanted one on one time with there bf/gf, and they spoke to me every now and then but I was alone. Then one of my friends bf is so rude and asks why I don’t/ have never been in a relationship and laughed.And I have been having that conversation with myself ever since I left high school last year, and I just awkward laugh when people bring it up but I don’t want to talk about it cause now I’m starting to think something is wrong with me cause no one ever seems to be interested in me. And I’m just a little upset/ embarrassed that everyone knows I’m 18 still haven’t been kissed or in been a relationship. And I over think all the time but it’s really starting to make me feel low, even though I know I shouldn’t be.