I have been practicing what I believe is insight meditation for over 5 or 6 years now in the Mahasi tradition but still very frequently I feel like I'm not doing it right or something.
You are practicing for 5-6 years but was it like 1 hour sitting every day for 5 years? Did you do any 10-day retreats? In all those years did you spend any days solely for meditation? If you have been doing it for that long, let's assume you have learnt the instructions and you are doing it right.
I suppose I thought that I would see some kind of change or have some insights but nothing much has changed and I can't say I've had any insights into the true nature of reality which is so often emphasized and mentioned.
The path of spirituality does not work like ordinary marketplace logic. Besides only doing insight meditation will not bring any significant change. Meditation or 'Right Mindfulness' is just one of the fold of the eightfold path of the Buddha. If you want to see a significant change then you have to follow the eight-fold path, you don't have an option of being selective.
I've started to do body scans but I'm unsure if I'm doing it right. I sit for a while and notice the breath then I start at the top of my head and go down the body part by a part ie crown of the head, back of head, forehead, eyes, nose, lips, chin, neck etc. But I have difficulty with this. I'm unsure how to focus on a body part apart from trying to see it in my mind.
After 5 years of practice, if you are still unsure and having difficulties with practice I will suggest you change the meditation you are doing. Samatha meditation is relatively easier and Zazen is what I will recommend to you.
Please don't tell me to read the scriptures or find a teacher. The scriptures bore me.I'm not a religious person. They are just so repetitive and convoluted that I don't find them helpful. They send me to sleep and trying to find a teacher is impossible. I have attended Sanghas regularly on occasions and nothing ever comes out of it. I don't know how to approach people and say can you please be my teacher. The people at the Sanghas didn't seem to be open to having students.
I see your problem is not as much as of the practice as much as it is about the frame of your mind. You have failed to understand the context of Buddhism and you have directly jumped to practice and expecting results. From your overall question, I understand you have missed studying the practice of, 'let-go', of not having 'Expectations', the importance of getting instructed about Dhamma along with meditation.
I agree that if you start reading the scriptures of Pali canon it's repetitive and at times boring, but there is an option available, and that is reading the commentary. I reckon you read the book, 'In the Buddhas words' by Bhikkhu Bodhi, that will put you in a greater context of Buddhism which will guide you towards the experiences you want.
If this is still boring to you, I will suggest that you read a few books by Ajahn Brahm, he is a Cambridge graduate in Physics, his words might resonate with you. And if you are hell-bent on having spiritual experience only through the medium of instructions on Meditation, in that case, I will suggest you read, Ajahn Brahm's book, 'Mindfulness, bliss and beyond', no boring scriptures straightforward instruction manual which takes you to la-la land.
About the teacher part, you really don't have to deal with real world people now that the internet is there. There are a plethora of videos on youtube teaching you the basics of Buddhism putting you in the right context. Watch Ajahn Brahms videos on youtube.
You don't have to approach anybody and ask to become a teacher, it doesn't work that way. A teacher is usually a highly ordained monk who professes to be a teacher, by himself or herself. Don't rely on people if they are not around you, the internet is there.