Hijacked Server Traffic

Is it possible that someone on the same network as my server (shared hosted, freebds) could somehow cause my traffic to be diverted to a new url after visitors landed on my website?

I assume this person has access to my home PC also and is reading what I type here etc. Has the ability to allow domains and IP's and divert others on my server, IS in the position to know who to allow and deny (my affiliates, customers etc IP's are recorded etc)

IF this was possible, how would I be able to catch this person out?

Where would I look for evidence of this and what am I looking for?

I don't manage my DNS and asking my server host (my suspect hosts with them too) gets a reply like: I don't understand what your asking? Do you need webaliser stats?

How would someone be able to do what I'm guessing is happening: That people can land on my site.. however, this guy can than redirect them to his own paying page. If I set a link here to my site..he'd soon add its domain to "allowed" etc etc.

I'm thinking I need access to server access to my dns, login info and Last Modified details on those file. I don't have these. I don't know what I'd be looking at if I had them.. and my server tech hasn't offered to look at such things.

My interest is more than intellectual.

Until last weekend my 2 1/;2 year project that has grown in sales volume beyond my expectations. I had had no contact with this person for 8 months and in that time sales where consistent. I Had changed all accesses, IP etc etc. I used to host with him. Then moved hosts since I didn't trust him (same problem back then - sales fell to nothing but traffic grew) moved to my current host.. not long after find HE is now on that host too.. now after I have contact from him again, sales have gone flat without any explanation, even though traffic has increased! 1:300 has become 1:10000 and I have checked everything site side (I'm a webmaster for over 10 years)

I'll be ruined very shortly and I don't know what to do.