Constipation. Or what we have to do?

My son will completed 2 yrs in May. Now I am trying to potty train him . He is not able to say his urge to going toilet but when I took him in toilet he can able to pee and sometimes when I am busy in my household work then he pee in his underwear . He ate in last 4 days oats, mushroom, chicken, spinach, sweet potatoes etc. drinks 12 oz milk per day and drank lots of water . But last 4 days he didn't do potty and also no smell comes or no gas in his stomach . Is that normal or what we have to do? He ate lots of fruits purée in last four days like mangoes , blue berry, avocado, apples etc . He is a picky eaters so he doesn't like to eat anything so most of the time I fed him forcefully . His weight is 11 kgs. Thanks in advance