K.M.
Hi Aleisha,
First off- this is not your fault. Don't stress yourself with that idea since stress can majorly effect your supply. You have done a wonderful job so far and I think it's great you are concerned about getting your baby the nutrients and love he needs.
Secondly, you mentioned he's not nursing as long, but is he nursing more frequently? If so, then there is definately no need to worry. He just wants smaller, more frequent meals. If he is NOT nursing more frequently, again I wouldn't really worry as long as he's happy. If you are feeding him solids of any sort, he won't NEED all the breastmilk he used to take, which means your supply *will* decrease. He's getting his nutrients elsewhere. This is not a bad thing and nothing to worry about, although he'll still need your breastmilk.
Some people will tell you babies don't wean themselves younger than one year. Not true. He could be deciding it's time for him to stop, even at this early age. I *KNOW* how hard it is. My daughter weaned herself (not a nursing strike, etc.) at 8 months. I cried...a lot. It was horrible for me since I wanted to nurse her for several more months & the bonding experience was like nothing I've felt before. Unfortunately, babies are on their own schedules and I'm slowly learning that I've got to let these milestones take place and accept them as a wonderful sign that my daughter is developing beautifully.
I wouldn't mix the milk with Pediasure. It's not beneficial for his health or development in this case.
Re: waking up to eat at 5. That's pretty normal, especially if he's going through a growth spurt, teething, or maybe just wating the extra snuggle time with mommy.
In any case, don't be hard on yourself if he decides he's done nursing or if you can't continue for one reason or another. Don't get me wrong, I am a HUGE breastfeeding supporter and will do anything I can to nurse my new baby, due in November, well into her first year. I won't give up until I've tried everything, just as I did with my first. However, if it's meant to be that he needs to take a bottle, use that time to be close to him. He can still lay in your arms. I hold my daughter's bottle for her, that way I ensure the quiet mommy/baby time is still there.
Good luck and don't ever feel bad. You've given your baby a wonderful gift!