Since learning organ was something I did later in life (I'm firstly a pianist), I can relate to the mental strain it was to play notes with hands and feet, and moreso with the left hand.
This puzzled me a bit because I would say my pedalling at the piano is more sophisticated in terms of limb/digit independence than playing notes on the organ with the feet. But nonetheless, when I first started reading hymns and simple exercises it was like trudging through thick mud. It was mentally painful.
As others have said, keep practising. But do it with specific intent, addressing specific difficulties you have. I found 'Master Studies for the Organ' by William Cary to be very helpful (where it begins the hands and feet together studies), as it starts out very basic and increases in difficulty with deliberate intent with a specific goal in mind.
Eventually you'll get to the point where you don't even really think about your feet, but that requires laying some foundation of habit. For instance, immediately knowing what feet you'd use in a particular passage without consciously thinking about it. That takes time and practise. If you keep at it, in no time you'll be playing the Bach Trio Sonatas
I personally don't think it matters too much if you look down at the pedals sometimes. Some people say the same thing about hands on the piano and I think it's silly. There's no gain to never looking, although there is gain in not 'having' to look, so you should aim for that.