Well, I will be 48 soon and although I still have monthly periods the patterns have changed on and off over the last 4 years - spotting, length of period (still spotting 14 days later), heavy bleeding, light bleeding, 28 days to 37 days) each month was different and like you I worried/panic every time which made my anxiety sky high throughout most of the month thinking about it all the time, wondering when it would come and how long it would last and what it would be like etc. I know for a fact my anxiety made it worse and caused most of these problems. Unfortunately, I have a fear of doctors so unless absolutely necessary I won't visit one for me, however, I do see an excellent Naturopath and my Psychiatrist who I discuss these concerns with. My Psychiatrist is fabulous because she is also around my age so therefore would be experiencing the same symptoms perhaps and also she is into natural wellness. I know if she had any concerns whatsoever she would make me see a doctor and I do speak to her about these things because after all she did study medicine before becoming a psychiatrist.
There are three things I found to have helped regulate my period in many ways. One is going gluten free and dairy free. I did this for 3 or 4 months 90% strictly and my period was great. Have slipped in recent months and have started eating gluten and some/little dairy. Hadn't noticed a change until the last month or so after going off diet for at least 3 months. My last two periods didn't come until day 35/36, however, I was highly stressed and depressed after moving house and suburbs so that would have contributed also. I found out that I am gluten intolerant and dairy intolerant. Now, with some people they can eliminate these foods for some time and then slowly introduce a little bit back into their diet or perhaps have the odd gluten product without it causing any symptoms. Gluten can cause many many problems including the reproductive area.
The other product I used was a 'Menopause Free' tablets by Fusion which contained Vitex amongst other herbs. I bought this at a health food shop. I live in Australia so Fusion is a well known brand here but you may be able to buy it in the US or no doubt they will have something similar. I took 2 tablets daily and the change of period in the second month was incredible - day 28, bleeding/spotting for up to 7 days. Great stuff.
And the last thing that helped was taking regular anti-anxiety medication.
I would probably guess that at 46 you are perimenopausal which can start 10 years before you actually hit menopause. Also at what age your mother went through menopause has some influence on when you may actually go through it too, so the experts say.
At least you have seen a doctor and he/she has ruled out anything serious, so that in itself should make you feel somewhat relieved.
I know how you are feeling and I wish you all the best.