I'm aware that a gerund is used with "I am looking forward to.. ('to' is a preposition here). Are there
instances where a gerund is not used... example "I look forward to visit you next week". Please give me some examples of a gerund not being used, if any. Thanks. Eva
Nope, with "look forward to" it's always the "ing" form of a verb.

I look forward to visiting you next week
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Hi, eva, Thanks for joining us. Welcome to English Forums! Emotion: smile

Just offhand, between the infinitive and the gerund, it's been the infinitive lately that doesn't work in certain situations, and the gerund which comes to the rescue. (There have been a few threads recently on the subject.)
Others may come up with some counter examples.

I look forward to visiting you next week is fine, BTW. I look forward to visit you doesn't work for me.

Best wishes. - A.

Edit. Ah, yes. In a case where the verbal follows the indirect object, we use the infinitive rather than the gerund. "Mother told me not to come."
If you wanted to use a gerund here, you'd need to employ the relative pronoun.
"Mother told me that coming here would be a big mistake!"

Is this the sort of thing you were asking about?

Don't forget you can also say 'I look forward to my visit'.

Thanks. Just want to clear some misconceptions that I had at the back of my mind. Eva
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Thanks. Just some nagging doubts at the back of my mind that someone told me that there are variations. It's alright now, you all have verified what I wanted to confirm. Thanks again. Eva