Head problem

[cods68]

Hi all can anyone shed about of light on a head problem ? Last yr I replaced the head gasket had a new rad fitted as well as the old 1 burst .... All was fine till about a month ago when I seen water in header tank on low I topped up to the full mark and sense then water leaks out over flow pipe and I had to keep toppin up  I did notice slight leak in rad but thought that's been there for awhile .... Sense then rad blew .... I sent it bk and they said there prob elsewhere as rad was fine ..... Aa bloke said it was faulty when he came to rescue .... Now I put another rad on and found head blown again ....  .... So bk to drawing board .... Would toppin up water have caused this As it was fine b4 .... And do I have to have head skimmed again ? Any light would be great Neil