It was a week ago now since i start getting very low traffic (not more than 25 visitors a day).... Before im averaging 60 - 90 visitors a day, there are weeks that im averaging 100 visitors a day. What happen?

Here is my blog URL
http://musclepain101.blogspot.com

Need your advice, guys....

Kind of impossible to answer without more info.

Can you elaborate?

I guess you better start doing SEO double time.. try article submission, participate in social networking, submit in different social bookmarkings, comments with related blogs. Try those and see result in a weeks or so.. Hope those help you..

You can just expect traffic to turn up at your site in the early days, you need to actively promote it to begin with.

It takes alot of hard work to start a successful blog!

This can be caused by many reason, such as
1. content : post reduce or quality drop
2. SERP: Your major keyword are drop on SERP
and etc..........

I suggest you to keep on promote your blog through SME and work out your SERP & Content to increase your traffic.

Your blog hurt my eyes, the dark colors for a health blog?
And the ads of pills etc. which are given more preference than the original content in the top, they don't look good and makes a visitor run away and never come back.

Blog traffic fluctuations are normal. You have to consistently write great and useful blog posts to hook regular readers to come back for more (and maybe even subscribe to your blog feed).