Originally Posted by carleton

Take the money you saved by buying a bike sight-unseen online and go to a shop and get a basic or in-depth bike fitting. That's what bike shops are for. Not only do they sell bikes, they offer services.

There in nothing that we (the internet) can do but guess as to what's going on.

If you don't think it's worth it, bear in mind that you will probably spend more money buying random parts (some of which you've already mentioned) trying to solve the problem...and even then, may not do so.