Grouping SUMS by Date in PostgreSQL

I'm trying to get a total of the grouped requests by date as follows

SELECT 
       sum(pit.preco) AS preco,
       sum(pit.quantidade) AS quantidade
FROM cliente c
LEFT JOIN erp_pedido ped ON ped.id_cliente = c.id_cliente
LEFT JOIN erp_pedido_it pit ON pit.id_pedido = ped.id_pedido

WHERE ped.tipo = 'C'    
  AND ped.id_cliente = 2

GROUP BY 
         ped.data_inicio ,
         c.nome,
         ped.id_cliente

ORDER BY ped.data_inicio desc,
         ped.id_cliente 

This results in

2017-03-01 00:00:00  ;  CLIENT NAME  ;  2  ;  1.5000   ;  209.0000
2017-02-01 00:00:00  ;  CLIENT NAME  ;  2  ;  3.0000   ;  418.0000
2017-01-01 00:00:00  ;  CLIENT NAME  ;  2  ;  4.5000   ;  627.0000
2016-12-01 00:00:00  ;  CLIENT NAME  ;  2  ;  6.0000   ;  836.0000
2016-11-01 00:00:00  ;  CLIENT NAME  ;  2  ;  7.5000   ;  1045.0000
2016-10-01 00:00:00  ;  CLIENT NAME  ;  2  ;  9.0000   ;  1254.0000
2016-09-01 00:00:00  ;  CLIENT NAME  ;  2  ;  10.5000  ;  1463.0000
2016-08-01 00:00:00  ;  CLIENT NAME  ;  2  ;  12.0000  ;  1672.0000
2016-07-01 00:00:00  ;  CLIENT NAME  ;  2  ;  13.5000  ;  1881.0000
2016-06-01 00:00:00  ;  CLIENT NAME  ;  2  ;  15.0000  ;  2090.0000
2016-05-01 00:00:00  ;  CLIENT NAME  ;  2  ;  16.5000  ;  2299.0000

I expected it to add up separately for each date and not add everything sequentially, it should look like this:

PRECO   ; QUANTIDADE
1.5000  ; 209.0000
1.5000  ; 209.0000
1.5000  ; 209.0000
1.5000  ; 209.0000
1.5000  ; 209.0000
1.5000  ; 209.0000

What am I doing wrong?