Malware? webmaster reports? help a clueless guy!

Hello.
I have a small fitness website using wordpress. Over the last few months (maybe even longer) I have been getting the occasional email from google with something along the lines of:

Dear owner or webmaster of https://www.bodybuildingdatabase.com/,
We are writing to let you know that some pages from https://www.bodybuildingdatabase.com/ will be labeled as potentially compromised in our search results. This is because some of your pages contain content which may harm the quality and relevance of our search results. It appears that these pages were created or modified by a third party, who may have hacked all or part of your site. Many times, they will upload files or modify existing ones, which then show up as spam in our index.
The following are some example URLs which exhibit this behavior:
https://bodybuildingdatabase.com/wp-includes/css/cvbnm-asdfghjkl-qwertyuiop

(that was the most recent email I got just over 2 weeks ago now)
I am forever looking for solutions online and trying to follow guides etc but I am not very well educated in things like this, in other words I don’t have a clue what I am doing. I have had things like this happen in the past but I used to just search on sucuri.net which usually pointed out the problem to a degree. When I search my website on there now (www.bodybuildingdatabase.com) it seems to be fine- no errors. However if I search https://bodybuildingdatabase.com/wp-content it says the following :
Unable to properly scan your site. Site empty (no content).

I do not really know what to do in this kind of situation I am not even sure if that is related or something completely different.

I am unsure what kind of details to write down here as I do not know what kind of details you guys need to know to hopefully help me out in this situation. On google webmasters tools under the crawl errors page it does say ‘2 not found’. Under the ‘fetch as google’ section it has a list of pages, most of which have a green tick next to them but 3 have a yellow sign saying denied by robots.txt, these seem to be the pages such as https://www.bodybuildingdatabase.com/wp-includes/…https://www.bodybuildingdatabase.com/wp-includes/css/ and https://www.bodybuildingdatabase.com/wp-includes/css/cvbnm-asdfghjkl-qwertyuiop

I have noticed over the last few weeks my page views for my website seem to have dropped a fair bit.

As I say I am not great with this kind of thing and I didn’t want to post this up as I am sure people have asked this before but from my searches on here I was just confusing myself more and more whilst getting very frustrated so I decided it was time to just ask for help!

So anything you can suggest is greatly appreciated.
Thanks