Ok, So I bought my bike off CL and it was in mint condition apart from the cranks. The guy told me the creaking was from the old pedals so I was like whatever I was gonna use my cages either way. So after changin them the noise continued but now its sound more like BB issues with bearings. Then when I was practising riding backwards and put alot of pressure on the cranks it felt like something in my crank slipped/spun backwards for a split second. what should i do?