Of course not all particularly vivid dreams must necessarily be of a prophetic nature, although some obviously are and only time will tell if this is one of them (and how much).

Even if it does not eventually become your future, you may on the other hand be seeing only one of many which are possible. Which version goes on to become your actual future depends largely on the series of conscious decisions which you continue to make in the present moment, which is your only true point of personal power to influence your own destiny.

It is also quite possible and quite normal for a dream to contain certain elements which relate to real world experiences, past, present and future, as well as others which bear no direct relationship whatsoever to what has already happened, is happening now or will mostly likely happen some undefined time from now.

Our dreaming mind or inner dream director often presents us with truths that we are either unable or unwilling to accept in any other form while we are fully awake, using unconscious symbols which represent something completely different in our waking lives.

Because these nightly dream scenarios have been produced by our minds and not someone else's, they are often written in our own almost unique language which may have some things in common with other people but may also mean that some things will have a very different meaning to when compared to what they will mean to someone else.

Amongst what could I agree be precognitive information I sense certain longings common to your age group (to eventually start your own family), as well as possibly some more personal issues related to the image you hold in your mind of your own body and how much weight you are carrying at the time.

I do not know exactly how old your cousin is relative to yourself, but I also sense a definite hint of jealousy with this dream that your cousin may appear to be having much more success than you are with regards to both having her own family as well as being able to better control her weight.

Interpreting dreams (either your own or someone else's is more of an art than an exact science, and it is quite easy to jump to premature conclusions about the possible significance of each specific dream element on the basis of one isolated case. Frequently alternative or even deeper meanings do not fully reveal themselves to us until we have had a series of dreams over the space of several nights, weeks or months from which we can hopefully become more aware of the bigger picture.

In the end we are each generally the best possible interpreter of our own dreams, but it is often valuable and enlightening to gain further intuitive insights from others in order to make our task a little easier than it otherwise might have been than if we had gone it entirely alone.

Just as readers often consult other readers presumably because they are too close and therefore also possibly too emotionally involved with the outcome of their own reading to be able to look at it objectively and without allowing their stronger emotions to get the better of their judgement, it is similarly frequently useful to get an outsider's viewpoint as well to help you on your way to discovering why you may have had this type of dream in the first place.

My own experiences as both a reader as well as someone who enjoys assisting others to explore their dreams in more detail is that often what appears on the surface to be the overall purpose of a specific message or dream turns out with the passing of time to be only one of it's many different purposes and subtle shades of meaning.

In other words you could indeed be spot on by recognising that your dream may contain a preview of your future, but I strongly suspect that this is only a small part of the whole story which your dreaming mind is currently presenting you with.

It is in my considered opinion rarely as simple as it might first appear to be.  

EoT

Dreaming of putting on weight may mean that you need to pay attention to your ego.  You should be more caring of other people, and not just yourself.  You aren't necessarily a bad person, but your higher self is telling you that you are being more self-centered than usual, and that you need to re-access your character, and how beautiful you are on the inside.  This will keep you from digressing spiritually.