Ive looked at your portfolio and read your forum posts on macro to get a sense of what your doing.
Yes, - its normal to have to get used to macro and take many many shots that will look soft, blurry and its easy to get discouraged. That macro lens doesnt make taking the shots any easier, - its a tool you need to learn to use.
The Tamron 90mm is an excellent macro lens btw.
Its worthwhile getting to understand some basics, then practice using what you know. Macro means large, not small, and what macro photography means is to make small things large. So you are magnifying subjects by getting very close to them. You can fill the lens with a an insect, or get close enough to show only s single stamen in a flower.
First thing to remember is that when you are close to the subject, and you are magnifying it, the tiniest movement of either the camera OR the subject will ruin the shot, as tiny movements are magnified. So tip #1 is use a tripod. Tip # 2 is to use a remote shutter release, or the self timer to you dont cause even the slightest movement in the camera by pressing the shutter.
Start with indoor subjects, like flowers where theres not breeze to cause movement.
Next thing to know is that the closer you are to the subject, the shallower the depth of field is.
See dofmaster.com for a good read on this and you will understand.
Essentially this means that at f/2.8, which is the largest opening for the aperture on this lens, the distance from the camera that is sharp to the end of that distance, - i.e. the depth, is extremely small, - in the range if millimeters.
This will work to your advantage as you can isolate a single flower stamen and have the rest of the flower blurred, - one of the traits of macro shooting. This also means that when shooting a subject with depth, - even a 1/4 of an inch such as a fly, you need to use a really small aperture size, - like f/11 and up. The bigger the number, the smaller the aperture (hole) size, and the greater the depth you can achieve.
You may notice that many good macro shots of butterfly's for example are all shot from the side, so the need for depth is minimal. Id you try a macro shot of one of these requiring depth of say 2 inches, you will end up with part of the insect sharp and part blurred.
next thing to think about is, - the smaller you aperture, the less light will come through to the sensor, therefore the slower the shutetr speed will be to allow more time for the light. This is whay you need a tripod, or a support, and you need to become familiar with increasing your ISO setting to allow reasonable shutter speeds.
Basically, set you camera to Aperture priority; set the aperture value to f/11; use MANUAL focus (important); set ISO to 100; take a shot using a tripod. See the result, then take more shots sing smaller apertures without touching focus or ISO. The to the same with higher ISO settings, and you will get a very good "feel" for whats going on.
Wish you luck, and look forward to seeing progress.