Why is there no hot water?

Ok... Im havng issue's with the hotwater in my bathtub. Problem:little hot water coming out. Recently whn i shower the cold water shoots out like a bullet but once i turn the nob to hot water it dripps.. Its pretty annoying and takes forevr to bath. This has just startd tho.. Before it was working fine and just up to a week ago it seems to be fading more n more. Any help? Advice? Im not running water elsewhre from the house while using the shower. So thats ruled out... New boiler ... Which is about 1.5 year old. .... Help?