Hi Suzy Kate
I am sure you will achieve your goal in the 16 months!! You have a great thing motivating you... Congratz on being engaged to get married by the way!!
About the headaches and tiredness, it is different for everybody... not everybody expierences these. My CDC told me if you have a headache it is ok to take a pill and rest a bit, just take the painkiller with a shake so its not too hard on your tummy. I haven't had any major headaches yet... but I am only on day 3. As for the tiredness I haven't had that at all yet.
Now that pesky bad breath... what I did was buy a travel tooth brush with tiny toothpaste, mouthwash and sugar free breath spray! I put it all in a small make-up bag together with some tylenol extra strength. I call it my CD survival kit

For motivation I have a list of reasons not to cheat hanging on my mirror in my room, and pictures of myself in my bikini stuck to every food cabinet in the house. (a bit extreme but I am somewhat of a binge eater) And just like Kels said about the size 10 dresses.... Yesterday I did a little shopping for dresses that are too small for me. (Good idea by the way Kels about hanging them around your room!)
Like I said I am only on day 3 but I prepared myself mentally for the CD and got a lot of information on what to expect from this forum, not to mention the marvelous support!
So just so you know there are alot of people here willing to support you and encourage you on your journey!!