It’s not that different man. You used a narrower comb in the recent picture which may have made it look a little thinner because your hair is very fine. This kind of part is really common with men and women who have fine hair but aren’t losing it.
Fine hair is a b**ch. Especially dark fine hair as your scalp will stand out much easier. Use some dry shampoo and it will help a lot both in making it more manageable and with volume. Too much conditioner will make it look like that, too much oil make it look even worse f*****g terrible, the longer the hair is the less room there is for error. More length means more it weight, more oil, and greater chance it sticks together resulting in what your picture shows or worse...
You could be diffusing, but it’s hard to say. Absent other symptoms though, I’m inclined to think it’s just the way your hair is.