In my neighborhood police will just stop you on the street for no reason and search you. Is there anything I can do about this?
Yes. If the police approach you, try to attract attention to yourself. Shout Hello! to a stranger, calling him by a name. Police will be more likely to go by the book if they think witnesses are present. To questions such as "What do you have in that bag?", just answer that it’s private and state loudly that they do NOT have permission to search you. They are permitted to pat the surface of your clothes for anything that might be a weapon (this is called a "Terry" search), but not to go into pockets to explore objects that could not be weapons.
If you see the police approaching you long enough in advance, you might dial your home number on your cell phone and put it on speaker phone. Whatever is said can be recorded on your home voice mail for defense use later if you are charged or if you wish to make a complaint of illegal search. Only you can decide whether your life will be better off after having done so, though. It may well just make your problems worse.