FSM problem

Sorry for late reply and thank you for your replies. After some tests I found problem and rewrite the code but this time I got some errors.

Error (10028): Can't resolve multiple constant drivers for net "xy_reg[1][1]" at VGA.vhd(255)

Error (10029): Constant driver at VGA.vhd(241)

The problem is not in state machine's cases at this time but I dont minimise the code anyway. When I erase the line underlined below, It kinda works but not enough. I know your ideas will be very helpful.

type XY_REG_TYPE is array (0 to 19,0 to 9) of std_logic;
	type AB_REG_TYPE is array (0 to 3,0 to 3) of std_logic;
	type XY_NEXT_TYPE is array (0 to 19,0 to 9) of std_logic;
	type AB_NEXT_TYPE is array (0 to 3,0 to 3) of std_logic;	
	type STATE_TYPE is (count,zero,left,down,right);
	signal m : integer range 0 to 9;
	signal n : integer range 0 to 19;
	signal c,d : integer range 0 to 3;
	signal ab_reg : AB_REG_TYPE;
	signal xy_reg : XY_REG_TYPE;
	signal ab_next : AB_NEXT_TYPE;
	signal xy_next : XY_NEXT_TYPE;
	signal state_reg, state_next : STATE_TYPE;
	signal T_reg, T_next : integer range 0 to 10; 
	begin
        TimeDelay : process (clk)
		variable cnt : integer range 0 to 10 := 0; 
		begin
			if clk'event and clk = '1' then
				if	EndOfField = '1' then
					if cnt = 10 then
						Delay <= '1';
						cnt := 0;
					else
						Delay <= '0';
						cnt := cnt + 1;
					end if;
				end if;
			end if;
		end process TimeDelay;
		
		FSM1 : process (clk, reset)
		begin
			if reset = '1' then
				state_reg <= count;
			elsif clk'event and clk = '1' then
				for n in 0 to 19 loop
					for m in 0 to 9 loop
						if xy_reg(n,m) = '1' then
							state_reg <= state_next;
							xy_reg(n,m) <= xy_next(n,m);
						end if;
					end loop;
				end loop;
			end if;
		end process FSM1;
		
		FSM2 : process (SW(1), BUTTON, Delay, xy_reg(n,m), state_reg)	
		begin
			for n in 0 to 19 loop
				for m in 0 to 9 loop
					if xy_reg(n,m) = '1' then
						state_next <= state_reg;
						xy_next(n,m) <= xy_reg(n,m);
							
						case state_reg is
						when count =>
							if Delay = '1' and SW(1) = '1' then
								state_next <= zero;
							else
								state_next <= count;
							end if;
						when zero =>
							if BUTTON = "111" then
								if n <= 18 then
									if xy_reg(n+1,m) = '0' then
										xy_next(n+1,m) <= xy_reg(n,m);
										state_next <= count;
									else
										xy_next(n,m) <= xy_reg(n,m);
										state_next <= count;
									end if;
								end if;
							elsif BUTTON = "101" then
								state_next <= down;
							elsif BUTTON = "110" then
								state_next <= right;
							elsif BUTTON = "011" then
								state_next <= left;
							end if;
						when down =>
							if n <= 18 then
								if xy_reg(n+1,m) = '0' then
									xy_next(n+1,m) <= xy_reg(n,m);
									state_next <= count;
								else
									xy_next(n,m) <= xy_reg(n,m);
									state_next <= count;
								end if;
							end if;	
						when right =>
							if m <= 8 then
								if xy_reg(n,m+1) = '0' then
									xy_next(n,m+1) <= xy_reg(n,m);
									state_next <= count;
								else
									xy_next(n,m) <= xy_reg(n,m);
									state_next <= count;
								end if;
							end if;
						when left =>
							if m >= 1 and n <= 18 then
								if xy_reg(n,m-1) = '0' then
									xy_next(n,m-1) <= xy_reg(n,m);
									state_next <= count;
								else
									xy_next(n,m) <= xy_reg(n,m);
									state_next <= count;
								end if;
							end if;
						end case;
					end if;
				end loop;
			end loop;
		end process FSM2;
		Game: process (clk)
		begin
			if clk'event and clk = '1' then
				xy_reg(1,1) <= '1';
			end if;
		end process Game;