Are we all mental? Body dysmorphia

I was thinking today about our bodies and how we all have different perceptions of how we look mentally compared to how we actually do look physically.
Thinking about my friends, family and people I know I'm pretty sure there's a very small amount of them that would turn around and say that they are 100% happy with their appearance or body. I'm also pretty sure I've heard most of them at some point talk about getting "some work" done.
The reasons and causes would be different for each person it's probably not as simplistic as the media's portrayal of men and women having immaculate bodies and perfect airbrushed skin. Maybe not getting enough cuddles as a child or perhaps an abusive parental relationship where one parent spat venom and abused the other over some kind of body defect that was wrong in their eyes planting the seed for that child later to drag out of their subconscious and let inhabit their mind.
I kind of guessed that body dysmorphia is having a skewed vision of your body that affects everyday life but here's the Wikipedia definition. It sounds a lot better.

The definition of body dysmorphia on Wikipedia is as below

Body dysmorphic disorder (BDD, also body dysmorphia, dysmorphic syndrome; originally dysmorphophobia) is a type of mental illness, a somatoform disorder, wherein the affected person is concerned with body image, manifested as excessive concern about and preoccupation with a perceived defect of their physical features.[1][2] The person complains of a defect in either one feature or several features of their body; or vaguely complains about their general appearance, which causes psychological distress that causes clinically significant distress or impairs occupational or social functioning. Often BDD co-occurs with emotional depression and anxiety, social withdrawal or social isolation.[3]

Body dysmorphia is a type of mental
Illness? Like anorexia or bullemia? Are either of those things BDD? I don't know so I had a google for a definition and I found this on about.com/phobias

Body dysmorphic disorder is a type of somatoform disorder in which the sufferer becomes obsessed with an imagined flaw in his or her appearance. Those who suffer from the disorder have a distorted view of their own bodies. They may spend a great deal of time grooming themselves or even undergo repeated plastic surgeries in an attempt to “fix” the perceived flaw.

Although it is possible for those who suffer from this condition to become obsessed with almost any part of their bodies, some areas are more common than others; the skin, hair, nose and weight are particularly common.

Those with body dysmorphic disorder often seek reassurance from friends or family but are unable to believe those assurances. It is not uncommon for sufferers to become withdrawn and even stop leaving the house, due to their belief that others will mock their flaws. In extreme cases, sufferers have even attempted suicide. The condition is often linked to generalized anxiety disorder and obsessive-compulsive disorder.

This sounds more like what I thought it was. Yet no mention of mental illness but this time OCD has a factor, this seems to make more sense. But is OCD a mental illness? Hits google again... Apparently yes. It's a anxiety thing but yes it's a mental illness.
What level of fretting over something is normal and when does it become an issue that needs to be addressed by a professional? The reason I ask is because I've recently become a bit worried about my body, I'm 30 and have started to worry about my weight, probably unnecessarily. I'm pretty sure most people would kill for a belly as flat as mine, I'm a skinny guy but am terrified of becoming overweight. I'm 5"7ish and I weigh somewhere between 9 and 10 stone changing weekly. Nowhere near overweight. Yet I'm now doing an Ab workout this has also inspired me to do press ups and in the space of two weeks my arms are double the size. Yet I feel my arms are smaller than ever and my dream toned washboard looks bloated. I don't even want to bulk up, why am I doing this?
The more I look into it the more concerning it is due to the lack of or conflicting information available. I have a friend who is pretty damn muscly and goes to the gym a lot yet is obsessed with being "fat" and "too small" when he is neither.
Another friend who told me "shit Ben your arms are twice the size of mine" also works out at the gym. My arms were obviously nowhere near the size of his.
Almost all of the women I know are "fat" yet the girls who actually are overweight don't tell me this. They know and probably also suffer in a different way.
Do we all have mental health or is this just normal? Where is that line that we cross from just another person with a couple of body issues and when does it become a mental health or problematic issue?
Beats me, I'm just another skinny fat guy eating his way through life.