Guy complication - your advice & opinions!?

there's this guy who ive known for about 2 years now.. (I work with him).. im 18 he's 22..we used to hang out and then found out he liked me.. and I kind of liked him, but i kind of pushed him away.. just because i get like that when i find someone i like, i get really shy and i hate it! but now ive come to the point where i really like him and now he has a girlfriend whom he is really happy with.. and theyve been going out for 8 months now.. and they have their own appartment together..and engaged! BUT he still acts lik ehe likes me.. and gets all giddy and stuff.. and always looks at me.. and my way of dealing with it has been just kind of ignoring him.. like lately we havent even talked that much..ive gotten so shy around him.. and it seems INSANE to me that i really lke him, so i dont know if i should just tell myself whatever and give up on it or? cause it really does seem pointless to me, but i just seem to lke him too much to get over it.. but now i've come to the last straw after fnding out he's been engaged for about 2 mnths now..