The Samatha/Vipassana thing is complicated.
There are clearly suttas where the Buddha divides the two, others where they are integrated. Without going into some long textual debate, the practical reality is that there is an axis. The more one looks at things as being smooth, pleasant, analog, the more one is doing samatha. The more one looks at things as being discrete, individual, transient sensations and notices that suffering caused by the tention in the illusion of duality, the more one is doing vipassana.
That said, in real practice, nobody can stay totally to one side or the other, and, in real practice, people oscillate from one side to the other to some degree.
So, it is nearly impossible to do pure jhana in a samatha sense and not see some of the true nature of phenomena and gain insight, and it is also nearly impossible to be doing strong vipassana practice and not chance into the samatha jhanas at times. What happens more often than not is what is described in sutta MN 111 where we get into something jhanic and then see some of their true nature and then get into the next jhana and see some of their true nature.
In this way, we get into Mind and Body, which is very samatha in general terms, and then get into Cause and Effect and the Three Characteristics, which are very vipassana, then get into the early A&P, which is very samatha in general, then get into the later part, which is very vipassana, then get into Dissiolution, which is very samatha, then get into Fear, Mistery, Disgust, etc. which are very vipassana, then get into early Equanimity, which is very samatha, then get into late Equanimity, which is very vipassana, this all being a generalization.
Thus, they are at once different things and also integrated. I talk some about this in a video here:
http://vimeo.com/69475208So, if you are having the experiences you are having, those are clearly stages of insight experiences, regardless of what practice you are doing.
The stages of insight are very normal things to just show up, even in non-trained, non-meditating people, as is commonly reported here (as hundreds of people have posted about), and much more so in people doing various meditative practices, including those who are just trying to do samatha or jhanas or whatever they wish to call them.
Helpful?
Daniel