Probability is a strange thing. Although you are likely to see things averaging out in the long run, it would be extraordinary if you didn't see any fluctuations in the results -- in fact that would be the most surprising thing in any run of luck, good, bad, or otherwise.
So the first thing I would say about the above is that we can ignore the €1,000 win as a complete and utter fluke. For your level of investment at current odds you would expect to win a €1,000 prize every eighty years on average. You will quite likely never see another (although having won one already doesn't make you any less likely to win another in future draws -- that's a common misconception that people have).
The next observation is that even ignoring the €1,000, you were way ahead of the odds for May to October. Assuming you bought at end of April and were eligible to win from start of May, you were running at an annualised return of 2%. The average (before the November changes) was around 1.1% if memory serves me right. You got almost your entire annual average in just six months. So perhaps a more pertinent question is why you were doing so well until November, rather than why you have done so badly since! (although the answer either way is: random chance).
If your figures are up to date, then I think you are saying you haven't had a win for about 14 weeks on the trot. That's bad luck, but it's far from extraordinarily bad luck. Since the November changes, your €50k stands to win a €50 prize on average once every seven weeks. You've gone a little over twice that without a win. Here's a chart of the odds (specific to your €50k investment) of you winning each possible number of €50 prizes from 0-20 in the year starting November last:
Here's the data:
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| 0.0461% | 0.3545% | 1.3614% | 3.4857% | 6.6934% | 10.2825% | 13.1633% | 14.4439% | 13.8679% | 11.8354% |
| 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| 9.0907% | 6.3477% | 4.0630% | 2.4005% | 1.3170% | 0.6744% | 0.3237% | 0.1463% | 0.0624% | 0.0252% | 0.0097% |
If you were to only win once every 13 weeks, you'd win 4 prizes in a year. To get the odds of winning that number or less, sum all the bars from 0-4. You get 11.94%. That means you have a nearly one in eight chance of winning four or less times. If it happened I'd say it was bad luck -- you have a better than 7/8 chance of doing better -- but I wouldn't say it was outlandish. And it would mean most of your year would look pretty much as barren as the period since last November.
With this sort of draw, the odds are less "lumpy" the more you invest. The odds of getting near the average return are much better for €100k than €50k even though, counter-intuitively, the average percentage return is the same for both amounts. In statistical terms, the distribution in the chart above has a higher standard deviation from the mean than the equivalent chart for a €100k investment.
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