SOMEONE PLZ HELP :( blackberry curve 9300 problems?

[zain]

my blackberry 9300 worked fine for 3-4 days, i got a new battery for it today, just now its started giving me serious problems,it becomes extremely slow and pauses for about 10 seconds at random times.i stop receving whatsapp messages and later sometime i receive all the messages that i was supposed to receive throughout the day at once! when i click on browser, it comes up 10 seconds later, then when i click on it the second time,it comes up quickly, ive tried rebooting the phone and it doesnt solve the problem, it was really smooth earlier on but its become sort of rigid now. P.S : i dont have a memory card,im running on the internal phone memory and these are the apps ive downloaded: whatsapp,facebook,twitter,youtube,dictionary,weather trax,angry pigs,fruit slash,bbc news. the max amount of apps running on one time are 2, namely,whatsapp and facebook,please help me out i would really appreciate a helpful reply