Blender normal map invert issues

I'm pretty new to Blender, and to texturing as well. I've been working on a piggy robot model in Blender for some time, and I'm having some issues with texturing in Cycles. Specifically with the normal map. For some reason, Blender inverts half of my normal map on the model, which make the seams that are supposed to go inward are now sticking out (every line on the texture/normal map is supposed to be an indentation, like this, but without the lines being black, if you know what I mean: And this is what happens when i try to apply the normal map: Now i've tried to invert the green(y) and red(x) channel of my normal map in photoshop (with help of the nvidia plugin) but it turns the normal map slightly transparent, so when I use the png in blender, the whole texture becomes much darker (the material should be a glossy plastic material). After that I tried to see if maybe changing the normal map node from 'tangent space' to 'blender object space', and that made the seams work, but also darkened the texture again, like this:

I'm kinda lost as to what i'm supposed to do now.