You know you're obsessed with Transformers when:

[Jinto]

You hear Flawless by George Michael and in your head he's doing a duet with Soundwave.

[Hursticon]

Spout Transformers quotes as if they were everyday-common sayings.

[Tetsuwan Convoy]

You make the transformation noise whenever you sit down and stand up.

[KalEl]

Spout Transformers quotes as if they were everyday-common sayings.

oh no i do that!...

[loophole]

when you greet people in real life with " bah weep graaaaagnah wheep ni ni bong"

[griffin]

You know... there are people who will read much of what is in this topic and say, that's just normal behaviour for them.

And I'm not saying I'm one of them.

[GoktimusPrime]

oh no i do that!...

Who doesn't!

From my personal examples of obsession^devotion...
+ Been collecting Transformers continuously since 1984
+ I always wear Transformers apparel
+ Other people tell me that my brain is like a TF encyclopaedia
+ I almost always have a Transformer toy on me, whether it be a trip to the supermarket or a trip overseas.
+ I greet strangers with "Bah weep granah weep nini bong" (if they're wearing Transformers apparel of have a TF badge on their car)
+ I once organised a TF convention (and organised several TF booths/stalls at other conventions)
+ I've attended organised TF fan meets in 3 states and once overseas.
+ I'm currently in the process of self-learning Autobot language.
+ I frequently incorporate some Transformers references in my teaching.
+ My daughter has been constantly exposed to Transformers since she was born (literally). She's even developing her own play patterns, like making up her own fan modes! (She's created an "attack mode" for the dump truck My First Transformer); I've recently discovered that I need to carry 2 Transformers with me each time I go out with my family now... my daughter's no longer content to just watch me play with my toys, she wants to join in too (which she often does at home, but now she's insisting on doing so outside too!)
+ It's not a hobby... it's a way of life.

My attempt at translating French to Autobot:

You know... there are people who will read much of what is in this topic and say, that's just normal behaviour for them.

Guilty as charged, and damn proud!

[Sinnertwin]

You make the transformation noise whenever you sit down and stand up.

Gold

[Rodimus Prime]

When you look at anything and start to imagine how they would transform and where their limbs and head pop out of.

[Gofigure]

You smile and subconsciously experience feelings and emotions associated with warmth, awe, and the sense of being protected every time you see a big red semitrailer on the road