As someone who plays guitar in a band, I can certainly understand how important it is to hear your guitar while you are playing.
The simplest approach is as Laurence suggested, re-position your guitar amp so you can hear it. Of course Laurence also suggested that the rest of the band and the audience really don't want to hear you as much as you want to hear you.
You could also (as you suggested) mic your guitar cabinet and run the signal from the mic directly into the powered monitor wedge (or if your guitar amp has a jack to output the signal - directly from the amp to the monitor without a mic). This is the next simplest approach.
But with simplicity you may be sacrificing utility and practicality! Both of these simpler methods will result in you hearing more of your guitar, but to the exclusion of your ability to hear anything else. In other words, to your ears your guitar will overpower everything else in the mix.
When playing in a band, it is important to hear what the other musicians and the vocalist are playing (or singing) - in addition to what you are playing. Otherwise, you run the risk of playing something that is not in sync with the rest of the band. Perhaps they go into the bridge one measure sooner than you thought they would or start the next verse without repeating the transition like you expected. Or their timing may vary slightly from what you expect and you might need to adjust so you are playing the right notes over the chords the other musicians are playing at the time.
In order to achieve the optimal balance between hearing what you are playing and what the rest of the band is playing, your best bet is to run the signal from your guitar amp into the mixing desk and from there to your active monitor. Then the overall mix of your guitar to the rest of the band can be adjusted to your liking and the overall volume of said adjusted mix in your monitor can be controlled by the volume control on your monitor. This is assuming your mixing desk has independent control of the monitor mix separate from the main mix as most decent mixer's will.
If your guitar amp or cabinet does not have a direct output to run to the mixer, you will need to mic it. Some guitarist simply drape a mic over the top of the cabinet by the mic cable. Best results can be achieved by using a dedicated instrument mic (such as a Shure SM57) with a focused pick up pattern on a short adjustable mic stand placed in front of your cabinet such that the mic can be positioned for optimal pickup of the guitar cabinet with minimal pickup of extraneous sounds.
You will want to experiment with different mic placements because the sound of your guitar in your monitor will vary depending on mic placement. Generally, placing the mic pointing at the center of the speaker will give your guitar a brighter tone and placing it to the side, a bassier, darker tone. You will also get a different tone by angling the mic (off axis) towards the amp speaker than you will pointing it directly at (perpendicular) to the speaker.
With a little experimentation at your next band practice, you should be able to achieve your goal and be able to hear as much of your guitar as you need (so your brain can confirm you are playing the right notes) and still hear the rest of the band. Good luck!