Hi there, it's not about if holding shopping carts is bad. Honestly they're fine. There are NO studies that are going to tell you that holding shoppingcarts is healthy, because of the fact that there's no reason at all to do such a study because holding them is harmless.
Now listen because this is important, I used to have severe OCD and was especially scared of dirty things. I used to spend at least 5 hours a day washing my hands, taking showers, and all kinds of other OCD things. However I don't have OCD anymore. You should start some cognitive behavioural therapy.
the thing about OCD is that right now it's enabling you from doing things. and probably making you really scared and anxious. Please try the therapy and I will give you some tips as well:
1. first of all, sometimes it's okay to be scarred, the thing is you just have to let the emotions be. Don't give in to them (this will make you even more anxious at first, but:) eventually the anxiousness will disappear I promiss you. It could take a day, it could take a weak, it could take a month, but it will disappear.
2. Right down your fear, right down what you do about it and than right down why this isn't rational. Do this with every fear! The purpose of this is that OCD isn't rational and by rationalising it, the OCD will lose its power.
3. Confront your fears. The only way you will see that germs aren't dangerous is by confronting them. For instance, after you go shopping: don't wash your hands for a change. Again this will make you a little more anxious at first, but this feeling will fade and eventually disappear.
Once you get a hang of it, you will not only notice you're current fears fading, but you'll also notice you won't get scarred as easily of anything new.
Good luck with this, I really hope you can make it work!
Some SSRI's and also some other meds can help with these anxieties,in combination with therapy.Lily