First of all, welcome to the boards! Second, you are doing an excellent job as a mama choosing to give your baby the best start possible in life by breastfeeding.
Regarding the weaning ... babies do who truly self wean before 12 months are extremely rare. And unless mom is doing some encouraging, babies rarely wean themselves before 18-24 months.
Many times mothers (such as your SIL) will believe their baby is self weaning, when in fact it's something else entirely. The first of these things is a low milk supply. And the second is just normal developmental stages all babies go through. It sounds like you might be experiencing a little of both. My little one is also 7.5 months old and is so interested in crawling and cruising around that she is EXTREMELY distractible. We nurse in the dark room, do white noise, nurse lying down, etc, etc ... but her new world is just too darn exciting. This is really common in babies their age. Are you night nursing? That is one way to make up for the fewer day time feedings while your baby goes through this stage. And it is just a stage ... it's temporary.
This is an excellent resource regarding weaning, it talks in detail about the distractibility issue and the low milk supply. It also includes tips to avoid premature weaning:
Do babies under 12 months self-wean?
Also see: The Distractible Baby
Here us a quote from that site:
"Older babies tend to be distractible and want to be a part of all the action around them. Your baby may be more interested in learning about the world than in eating during the day (these same babies often increase their night nursing to make up for their busy days).
Milestone times, such as crawling and walking, and stressful times like teething or illness can also cause baby to be less interested in nursing - these types of things are common in the second six months.
One should understand that this is not self-weaning but a temporary developmental stage."
Remember, "this too shall pass." If you need any more help/support ... keep posting. And since our babies are the same age and going through the same issues, I'd be happy to chat anytime and "compare notes," so to speak.