Did you buy the cheapest or were you swayed by good marketing? Have you read a particularly persuasive artice in Runners World or similar?
In essence ....the best trainers are those that are comfortable and don't give you blisters, pinched toes or, worse still, numb toes. Ones that don's scrumch the ends of your toes or cause your nails to go black. What sort of foot type are you? What is a pronator or supinator? These are foot types and commonly referred to as flat feet or high arched. It is probably best to seek help either from a really good running shop if you recognise what foot type you are or else seek an evaulation from a physiotherapist who can video your running style, analyse your gait, go through it with you personally and then advise accordingly. If insoles (orthotics) are recommended these too can be discussed regarding relevance at the time of consult and an appropriate referral made. You can be assisted every step of the way. So what are the best trainers?? Those that allow you to "just keep on running"!