ok , make sure you bed the new ones in, when i switch from old to new i always get pains for the first few runs, so i take the pace right down and just jog a few miles in them 3 or 4 times or go on grass. i get really bad cramp in my calfs only occasionally on the end of my long runs, the worst being the end of a half marathon , the last two to three miles and that was definately fluid intake when i look back at what i did or didnt do.
Sorry but I am on a crusade on here to advise people to go get checked out properly by a sports physio...these forums are not read by qualified experts and i aint one. i use the physio and they have worked wonders on various ailments of mine and they have kept me running. it could be the wrong type of shoes, your style, your build, an old injury, your diet, speed , terrain etc etc etc...sorry if that sounded harsh but if people just went to them it would stop a lot of worries for runners old and new. they only cost 30 to 40 quid , the cost of an average meal for two!!
dont stretch it, that just tears the broken fibres that are trying to repair...ice and a bit of massage to get the blood in.get your gait analysed, you may have the wrong shoes completely and finally go to a sports physio for sake of 35 quid, you may have something else going on. if it was cramp, then the fluids would make sense but it sounds too bad for cramp.
instead of paying 20 a month for gym , pay the 35 quid for a decent physio who will sort you out, people think nothing of paying 35 quid for a meal or a t-shirt but if you want to stay fit and enjoy running then go to the experts. i have been 3 times over 3 years , once for knee tendonitis, then shin splints and then i felt a slight pain in knee again and could have carried on but went to physio who to my relief said tendonitis again, i self diagnosed on internet and thought it was a cartilidage probelm. its the worst thing you can do is this sort of thing on forums like this. dont get me wrong there is good advice on kit, training programmes etc but dont trust what anyone says on here when it comes to your body and what it might be. now go to the physio!