E.G.
hi E.,
i have had a similar problem with my daughter. she is 16 weeks old.
what i have learned is that some babies cry to let out pent up energy from the day.
she still does it from time to time. what i do is i just walk around with her, sometimes i will stand in one spot and just sway back and forth rubbing her back.
when my daughter was that age, she would just have her "fussy" time. but relax, it will soon pass. her doc said it was probably colic. put her on special formula and had special bottles.
have you tried swaddling her? i know that babies at that young of age sometimes like the comfort of that, it reminds them of being back in the womb.
i hope that this helps.
E.