a. I have gone there often.
b. I have gone there many times.
c. I have gone there frequently.
Is there a difference between the meaning of these sentences?
Don't a and c imply some kind of regularity?
'I've gone there' is not typical English usage. Common choices are: I've been there; I went there; I used to go there. I've been to London often (many times, frequently).
I went to (used to go to) London often (many times, frequently)when I was in England.
To your questions:
They mean pretty much the same, except that 'often' and 'frequently' are relative, and not necessarily 'many times'. To me, "I've been to London often" might mean 4-5 times (since I live in Australia).
'Regularly' has two usages. 1) Often, frequently. 2) With a fixed interval.
a. Last March, I watched the film 3:10 to Yuma many times.
b. Last March, I watched the film 3:10 to Yuma often.
c. Last March, I watched the film 3:10 to Yuma frequently.
Now, let's say that I have watched that film fifteen times in the space of three days in March. Would you use b or c in this case?
a. I wouldn't use b or c.
Let' say I have watched that films three times on the 2nd of March and four times on the third and five times on the 29th. Would you use b or c in this case.
I wouldn't use b or c in the past tense like this. I would in present tense though. I clean my teeth many times. Not correct, since you need to add a time frame. I clean my teeth frequently. Generally would mean about 3+ times a day. I clean my teeth often. Less specific. Could mean 'every day' depending on the speaker's understanding of 'often'.
I am aware that frequently and often are different from regularly, but I think they both carry the idea of frequency.
I agree that there's not a lot of difference between often and frequently.
They carry the meaning of regularly only if regularly is used in definition 1. of my last post.
If I visit my dentist regularly every year, that doesn't imply frequently or often. Similarly if I take a regular bath on the 1st day of every month.