Try adding high-fibre foods to all of your meals, not just breakfast, gradually building up the amount until you're eating at least 30g of fibre every day. Also, remember to keep drinking water throughout the day, as dehydration makes constipation more likely. Include some fermented foods as well.
Try chia seeds, butter beans (or any other beans that you like), chickpeas ground flax seed/linseed, nuts, kimchi, sauerkraut, kefir, Greek yogurt and so on.
Try to ensure that you are eating lots of different vegetables over the course of the week.
Cut down severely on, or completely eliminate, white and beige carbs. So, ideally no white bread, no white rice, nor breadcrumbed fish/chicken, cakes, pastries, biscuits, pizza or pasta. Instead have wholemeal bread, wholemeal pasta, wholegrain rice - and in modest quantities.
Try to avoid sugary foods and drinks.
In the mornings, a mug of strong black coffee might help things along as well.
I hope you get some relief soon.