As others have stated life is NOT always fair..You got 6 months of the BF..now go home and see if you can continue the relationship. Let him get settled in London then maybe apply for a fiance visa.
You are young and have a lot of time.
The high road doesnt always feel good but its the law...I hate driving 55 on a country road but I do it so I dont get a ticket.
I didnt plan on falling for an Englishman but I did and I am uprouting my life to start a new one but it wasn't a decision we took lightly and we are older and have the resources to allow us to do it and start life as we saw fit.
Working illegally is what makes it immigrants look bad in the US and the UK and this is why they crack down and yeah the others are right it may bite you in the ass. Your willing to lose a lot to live with him in London, would he do the same for you and move to the US? Follow the rules as much as it sucks but in the end if it is meant to be and you can overcome the hurdles it is sweet!
Good luck